Switchable electroactive devices for head-mounted displays

ABSTRACT

Embodiments of the disclosure are generally directed to systems and methods for switchable electroactive devices for head-mounted displays (HMDs). In particular, a method may include (1) applying an electric field to an electroactive element of an electroactive device via electrodes of the electroactive device that are electrically coupled to the electroactive element to compress the electroactive element, which comprises a polymer material defining nanovoids, such that an average size of the nanovoids is decreased and a density of the nanovoids is increased in the electroactive element, wherein the electroactive device is positioned at a distance from a user&#39;s eye, and (2) emitting image light from an emissive device positioned such that at least a portion of the image light is incident on a surface of the electroactive device facing the user&#39;s eye.

CROSS REFERENCE TO RELATED APPLICATION

This application is a non-provisional utility application which claimsthe benefit of U.S. Provisional Application No. 62/777,825 filed 11 Dec.2018, the disclosure of which is incorporated, in its entirety, by thisreference.

BACKGROUND

Projector screens include a surface such as a screen used for displayingprojected images and may often be composed of fabric or paints thatcontain granular structures. In some respects, the greater thegraininess of the screen, the more diffusely and uniformly the screenmay scatter light. In the field of optics, an ideal diffusely scatteringsurface may be referred to as a Lambertian diffuser. In particular, aLambertian diffuser may have the property of being able to distributeincident light equally over a 2π solid angle. This property may beuseful for projector screens, which may be used in home theaters ormovie theaters, at least because such projector screens may have largeviewing angle. However, conventional projector screens are notnecessarily switchable between a transparent state and a reflectingstate. Moreover, such projector screens are often used in large-scalesettings, for example, in a home or building, and are not typically usedin the context of wearable devices.

SUMMARY

As will be described in greater detail below, the instant disclosuredescribes switchable electroactive devices which may be used inhead-mounted displays (HMDs). In one embodiment, a display device isdescribed, the display device including an electroactive devicepositioned to be located at a distance from a user's eye when thedisplay device is worn by the user. Further, the electroactive devicemay include (1) an electroactive element including an electroactiveelement that includes a polymer material defining nanovoids and (2)electrodes electrically coupled to the electroactive element andconfigured to apply an electric field to the electroactive element,wherein the electroactive element is compressible from an uncompressedstate to a compressed state by the application of the electric field soas to decrease an average size of the nanovoids and increase a densityof the nanovoids in the compressed state. Moreover, an emissive devicepositioned to radiate image light onto a surface of the electroactivedevice facing the user's eye. The emissive device may be an ultra-shortthrow projector.

In some examples, the electroactive device may be substantially opaquein the uncompressed state. Further, the electroactive device may betransparent in the compressed state. In the uncompressed state of theelectroactive element, the nanovoids have a first average size on anorder of a wavelength of incident light. In the uncompressed state ofthe electroactive element, the nanovoids may have a first average sizeon an order of a wavelength of incident light. Additionally, in thecompressed state of the electroactive element, the nanovoids have asecond average size that is substantially smaller than the wavelength ofthe incident light. In the compressed state of the electroactiveelement, the nanovoids may have a second average size that issubstantially smaller than the wavelength of the incident light.

In some examples, the display system may further include an eyepiecepositioned between the user's eye and the electroactive device. Theeyepiece may be configured to modify a focus of the user's eye to afocal plane of the electroactive device in an active state of theeyepiece. The active state of the eyepiece may be used in a virtualreality application. Further, the inactive state of the eyepiece may beused in an augmented reality application or a mixed reality application.

In one example, the eyepiece may include a proximate eyepiece and thedisplay device may further include a distal eyepiece positioned near asurface of the electroactive device opposite the proximate eyepiece. Inone example, a degree of scattering of incident light by theelectroactive element may be based, at least in part, on at least one ofthe density or the average size of the nanovoids.

In another embodiment, a display device is described. The display systemmay include an electroactive device including an electroactive elementand electrodes electrically coupled to the electroactive element.Additionally, the display system may include a waveguide displaypositioned to be located between the user's eye and the electroactivedevice when the display device is worn by the user, the waveguidedisplay configured to transmit image light to the user's eye. In someexamples, the waveguide display may be configured to operate with alight source. The light source may include at least one of a microlight-emitting diode, a light emitting diode, an organic light-emittingdiode, or a laser.

A corresponding method is also described. The method may includeapplying an electric field to an electroactive element of anelectroactive device via electrodes of the electroactive device that areelectrically coupled to the electroactive element to compress theelectroactive element, which includes a polymer material definingnanovoids, from an uncompressed state to a compressed state such that anaverage size of the nanovoids is decreased and a density of thenanovoids is increased in the electroactive element. The electroactivedevice may be positioned at a distance from a user's eye. The method mayfurther include emitting image light from an emissive device positionedsuch that at least a portion of the image light is incident on a surfaceof the electroactive device facing the user's eye. In some embodiments,the method may additionally include reducing the magnitude of theelectric field applied to the electroactive element of an electroactivedevice to expand the electroactive element from the compressed state tothe uncompressed state such that the average size of the nanovoids isincreased and the density of the nanovoids is decreased in theelectroactive element

Features from any of the these or other embodiments may be used incombination with one another in accordance with the general principlesdescribed herein. These and other embodiments, features, and advantageswill be more fully understood upon reading the following detaileddescription in conjunction with the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate a number of exemplary embodimentsand are a part of the specification. Together with the followingdescription, these drawings demonstrate and explain various principlesof the instant disclosure.

FIGS. 1A-1D are illustrations of exemplary switchable electroactivedevices in uncompressed and compressed states, which may be used toselectively display images to a user's eye.

FIG. 2A illustrates an example diagram demonstrating Rayleigh scatteringby particles (e.g., nanovoids) that are smaller than the wavelength ofincident light, which may be used to explain why the switchableelectroactive device can reflect or transmit light in an uncompressed orcompressed state, respectively.

FIG. 2B is an illustration of an exemplary plot of the intensity ofscattered light from a particle (e.g., a nanovoid) as a function of theangle of incident light on an electroactive element in a switchableelectroactive device.

FIG. 3 is an illustration of an exemplary plot of the relative intensityof the scattered light as a function of size of a particle (e.g.,nanovoid), and may explain why certain nanovoid sizes are used foroptimal performance of the disclosed switchable electroactive device.

FIGS. 4A and 4B are exemplary graphical representations of the fractionof scattered light as a function of the density of particles in a volumeand as a function of particle size, which may explain why certainnanovoid densities provide for optimal performance of the disclosedswitchable electroactive device.

FIG. 5 is an illustration of an exemplary scenario demonstrating the useof a switchable electroactive device in an compressed (e.g.,transmissive) state for virtual reality (VR) and mixed reality (MR)applications.

FIG. 6 is another illustration of another exemplary scenario showing aswitchable electroactive device in an uncompressed (e.g., opaque) statefor VR and MR applications.

FIG. 7 is an illustration of an exemplary scenario showing a switchableelectroactive device in a compressed state along with correspondingeyepieces for use in VR and MR applications.

FIG. 8 shows is an illustration of another exemplary scenario showing aswitchable electroactive device in an uncompressed state along withcorresponding eyepieces for use in VR and MR applications.

FIG. 9 is an illustration of an exemplary scenario showing a switchableelectroactive device in a compressed state for use with a waveguidedisplay for use in augmented-reality applications.

FIG. 10 is an illustration of another exemplary scenario showing aswitchable electroactive device in an uncompressed state for use as aprivacy screen use in for augmented-reality applications.

FIG. 11 illustrates an exemplary method for operating the switchableelectroactive devices described herein.

FIG. 12 shows an exemplary augmented-reality system dimensioned to fitabout a body part (e.g., a head) of a user.

FIG. 13 shows an exemplary augmented-reality system including an eyeweardevice with a frame configured to hold a left display device and a rightdisplay device in front of a user's eyes.

FIG. 14 shows a head-worn display system, such as a VR system, thatmostly or completely covers a user's field of view.

Throughout the drawings, identical reference characters and/ordescriptions indicate similar, but not necessarily identical, elements.While the exemplary embodiments described herein are susceptible tovarious modifications and alternative forms, specific embodiments havebeen shown byway of example in the drawings and will be described indetail herein. However, the exemplary embodiments described herein arenot intended to be limited to the particular forms disclosed. Rather,the instant disclosure covers all modifications, equivalents, andalternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

Embodiments of the disclosure are generally directed to electroactivedevices and optical systems that selectively relay light from a displayto a user's eye. In some conventional virtual-reality HMDs, lightemitted by a display placed in proximity to the user's eye may betransmitted to the eye by an eyepiece. Accordingly, the display may bepositioned at an optical plane that is conjugate to the location of theuser's eye. The display may include a liquid crystal (LCD) display, alight-emitting diode (LED) display, a microLED display, an organiclight-emitting diode (OLED) display, a waveguide display, a liquidcrystal on silicon (LCOS) display, and/or the like. In contrast, thedisclosed systems may include configurations where a display may projectlight onto a switchable electroactive device serving as a screen thatmay selectively reflect a portion of the light to a user's eye.

The switchable electroactive devices may selectively reflect incidentlight via electroactive elements that may have adjustable opticalproperties based on an applied electric field. The electroactiveelements may include electroactive materials (e.g., electroactivepolymers, EAPs) having nanovoids, to be discussed further below.Further, the electroactive elements may be sandwiched by electrodes toform the electroactive device. The transparency or opacity of ananovoided electroactive element may be controlled through theapplication of a voltage across the electrodes. This application ofvoltage may modify the volume of the nanovoided electroactive elementand thus the average size and density of the nanovoids in theelectroactive element. In some examples, the electroactive element mayhave random or regularly dispersed nanovoids.

The nanovoided electroactive element may exhibit differential Raleighscattering, for example, based on the average size, density, and/ordistribution of the nanovoids. As will be further described below,Raleigh scattering may represent an underlying physical mechanism forthe change in a transparency of an electroactive element upon theapplication of a voltage.

Certain embodiments describe system architectures where light may beradiated by a projector onto a switchable electroactive device that isplaced at an optical plane that is conjugate to the retina of the user'seye. As noted, in some examples, the disclosed systems may control thetransmissivity, transparency, and/or reflectivity of the electroactiveelement in the switchable electroactive device. For example, thedisclosed systems may apply an electric voltage to the electroactiveelement by the electrodes of the electroactive device. This may allowthe electroactive device to be selectively turned on to serve as adisplay in one configuration, and to be turned off in anotherconfiguration to serve as a transparent device.

The disclosed systems may be used in connection with conventionaldisplays including, but not limited to, an LCD display, an LED display,a microLED display, an OLED display, a waveguide-based display, a LCOSdisplay, and/or the like, which are typically not transparent. Byprojecting light onto the switchable electroactive device from anoff-axis projector (e.g., an ultra-short-throw projector), the disclosedsystems may be used for mixed-reality, augmented-reality, and/orvirtual-reality applications (collectively referred to as “artificialreality” herein). The applicability of the disclosed systems describedherein for artificial reality applications may be determined at least inpart by various design parameters of the display and/or theelectroactive devices including, but not limited to, the switchingspeeds, power requirements, translucency, and/or the like.

In some examples, the projector may include an ultra-short-throwprojector positioned with respect to the switchable electroactivedevice. The ultra-short-throw projector and the electroactive device maybe configured in a HMD such that the HMD may selectively displayartificial reality content. Alternatively, a waveguide display orsimilar device may be used in conjunction with the switchableelectroactive device in the HMD such that the HMD may selectivelydisplay artificial reality content. In particular, the switchableelectroactive device may serve as an optical filter that may beselectively turned on and off to allow for ambient light to enter theeyepiece of the HMD and toward the user's eye. As such, the switchingspeed of the electroactive device may represent a design parameter ofthe HMD or similar device.

FIGS. 1A and 1B illustrate exemplary diagrams demonstrating a switchableelectroactive device (e.g., a screen) in a uncompressed state and in acompressed state, respectively. In particular, the electroactive deviceof FIGS. 1A and 1B may be configured to be opaque in an uncompressedstate of the electroactive element 100, and the electroactive device maybe configured to be transparent in a compressed state of theelectroactive element 100.

As shown in diagram 101, the electroactive element 100 (e.g., an EAP)may include nanovoids 110. For example, as will be described in greaterdetail below, electroactive element 100 may include a polymer material(e.g., an elastomeric polymer) defining a plurality of nanovoids 110.Further, the electroactive device may include electrodes 109 and 111electrically coupled to the electroactive element 100 and configured toapply an electric field to the electroactive element 100. Electrodes 109and 111 may include any suitable electrically conductive material, suchas, for example, an optically transparent material (e.g., a transparentconducting film including a transparent conductive oxide such as indiumtin oxide, fluorine doped tin oxide, and/or doped zinc oxide, aconductive polymer such as a polyacetylene, polyaniline, polypyrrole,and/or polythiophene derivative, carbon nanotubes, and/or graphene).Moreover, a voltage may be applied to the electroactive element 100using a circuit 121 that generates an electric field across theelectroactive element 100. In some examples, the electroactive element100 may be compressible by an application of the electric field whichdecreases the nanovoids' average size and increases a density ofnanovoids in the electroactive element 100.

Diagram 101 shows the electroactive element 100 in an uncompressed statein which the circuit 121 of the electroactive device applies no voltageor a relatively low voltage across the electroactive element 100 viaelectrodes 109 and 111. Accordingly, the nanovoids 110 may be larger insize with respect to a compressed state and may therefore scatterincident light. As noted, the uncompressed state of the electroactiveelement 100 (FIG. 1A) may correspond to the nanovoids having a size onthe order of a wavelength of the light, and the compressed state of theelectroactive element 100 (FIG. 1B) may correspond to the nanovoidshaving a size that is substantially smaller than the wavelength of thelight. For example, electroactive element 100 may scatter light havingwavelengths in the visible spectrum (i.e., about 380 to about 740 nm) orat least a portion thereof. Moreover, the degree of scattering ofincident light by the electroactive element may be based, at least inpart, on the density or the average size of the nanovoids. In someexamples, the size of the nanovoids may range from about 0.1 nm to about1000 nm. Further, the size range for the nanovoids (e.g., thepolydispersity of the nanovoids) may vary by a factor of about five ormore (i.e., the nanovoids may exhibit a diameter change of 5X or more)between the compressed and uncompressed states (e.g., the size range forthe nanovoids between the compressed and uncompressed states may vary bya factor of between approximately 2 to approximately 20 or more). Insome examples, the shape of the nanovoids in the electroactive elementmay include any suitable shape including, but not limited to, spheroidshapes, ellipsoid shapes, disk-like shapes, and/or irregular shapes, andthe nanovoid shapes may change between the compressed and uncompressedstates.

In some examples, the electroactive device may include a single pair ofelectrodes, such as electrodes 109 and 111, or multiple pairs ofelectrodes (not shown) which may be patterned across a region of anelectroactive element (e.g., similar to electroactive element 100). Inparticular, the region of the electroactive element may correspond to anaperture associated with the electroactive device as used in an HMD.This may be done in order to create spatially controllable lightscattering (e.g., scattering that is implemented with differingmagnitudes at different regions of the electroactive element). Suchspatially controllable scattering may serve to increase the dynamicrange of projected images scattered by the electroactive device.Further, while electrodes may serve to impart an electric field onto theelectroactive element and modify the electroactive device properties asdescribed herein, in other examples, the electroactive device may beswitched with at least a partially non-electrical technique. Inparticular, the electroactive device may be switched based on amechanical compression of the electroactive element or may be switchedusing acoustic waves that may propagate through the electroactiveelement.

Turning now to FIG. 1B, diagram 103 represents the electroactive element100 of the electroactive device shown FIG. 1A in a compressed state. Inparticular, the circuit 121 of the electroactive device may apply anincreased voltage across the electroactive element 100 via electrodes109 and 111. Accordingly, the disclosed systems may apply an electricfield (not shown) between the electrodes 109 and 111 of theelectroactive device. This may lead to the compression of the nanovoids112 as compared with their uncompressed state (shown and described inconnection with FIG. 1A, above). The magnitude of the electric field maybe configured to modify the extent of the compression of the nanovoids112. For example, the magnitude may be configured to reduce the size ofthe nanovoids 112 to be relatively smaller than the wavelength ofincident light on the electroactive element 100 (e.g., smaller thanwavelengths of light in the visible spectrum or at least a portionthereof), causing the electroactive element 100 to become relativelytransparent, thus allowing the incident light to propagate through theelectroactive element 100.

As the nanovoids are compressed, the size of the nanovoids 112 maybecome several orders of magnitude smaller than wavelengths of lightincident on the electroactive element 100. In this case, the amount oflight scattered from the electroactive element 100 due to the nanovoids112 may be minimized during compression. Further, the interaction ofelectromagnetic fields with nanovoids 112 having a size that issubstantially smaller than wavelengths of incident light may lead toRayleigh scattering of the incident light from the nanovoids 112. As thesize of the nanovoids 112 in the electroactive element 100 increases,the amount of scattered light from the electroactive element 100 mayalso increase. If the nanovoids 112 are in the same or substantially thesame size range as wavelengths of incident light, a Mie scatteringmechanism may describe the scattering of the light from the nanovoids112.

In some examples, when there is little or no electric field applied tothe electroactive element 100 by the electrodes 109 and 111, the size ofthe nanovoids 112 may be less than about 1000 nm and greater than about400 nm. As noted, the application of electric field across theelectroactive element may result in a mechanical compression of theelectroactive element 100 from a prior uncompressed state. The magnitudeof electric fields across the electrodes 109 and 111 can selected tochange the size and density of the nanovoids 112 to achieve a desiredamount of in transparency between the compressed and uncompressedstates. In a compressed state, the nanovoids 112 of the electroactiveelement 100 may be reduced, in the compressed state, to sizes of fromabout 0.1 nm to about 50 nm based on the magnitude of the appliedelectrical field.

FIGS. 1C and 1D illustrate exemplary diagrams 105 and 107 demonstratingan example of a switchable electroactive device in a uncompressed stateand a compressed state, respectively. In particular, diagram 105 showsincident light 114 scattering off the electroactive element 100 in theuncompressed state to produce scattered light 116 via a Rayleighscattering mechanism. As noted, this scattering may be due to the factthat the nanovoids 110 may have a size that is on the order of thewavelength of incident light when a voltage applied by a circuit 122(e.g., via opposed electrodes, such as electrodes 109 and 111 in FIGS.1A and 1B) is below a predetermined threshold. Further, the fraction ofthe incident light 114 may be scattered because the size of thenanovoids 110 is within about 0.1 to about 10 times the wavelength ofthe incident light 114. In one example, the fraction of scattered light116 can be anywhere from greater than about 95% to less than about 5% ofthe incident light 114 on the electroactive device.

Diagram 107 of FIG. 1D shows a compressed state of the electroactivedevice shown in FIG. 1C. In particular, incident light 118 may betransmitted through the electroactive element 100 to produce transmittedlight 120 when the nanovoids 112 are compressed to be much smaller thanthe wavelength of incident light 118. As noted, the nanovoids 112 may becompressed when an electric field is applied to the electroactiveelement 100 as a result of a voltage applied by the circuit 122.

In particular, if a beam of visible wavelength light (e.g., incidentlight 118) is directed towards the electroactive device when theelectroactive element 100 is in a compressed state, the electroactiveelement 100 may scatter relatively little light because the size of thenanovoids 112 may be much smaller than the wavelength of light.Accordingly, the electroactive device may be transparent in the visibleportion of the electromagnetic spectrum. In another embodiment, bymodulating the electrical field applied across the electroactive element100 as a function of time, the electroactive device can serve as aswitchable component, such as, for example, a switchable screen, atime-varying beam-block, and/or a time-varying intensity modulator forlight in the visible and near-infrared portion of the electromagneticspectrum. Further, as described in connection with FIGS. 5-8 below, ifthe electroactive device is placed in the vicinity of a user's eye in anHMD and a projector is positioned at a suitable location (e.g., anoff-axis location) with respect to the electroactive device, a systemincluding such components can serve as a near-eye artificialreality-based HMD.

FIG. 2A illustrates an exemplary diagram 201 demonstrating an example ofRayleigh scattering by particles having particle sizes (i.e., averagediameters) that are smaller than the wavelength of incident light. Asused with respect to Rayleigh scattering, particles may refer to thenanovoids in various electroactive elements described herein. As noted,Rayleigh scattering may explain why nanoparticles of a certain size mayscatter incident light in an electroactive element. In particular,incident light 210 may interact with a particle 212 (e.g., a nanovoid110 in an electroactive element 100 as shown and described above inconnection with FIG. 1A) and may generate scattered light 214 via aRayleigh scattering mechanism. As used herein, Rayleigh scattering mayrefer to a predominantly elastic scattering (i.e., without a change inphoton energy) of electromagnetic radiation, such as light, by particlesmuch smaller than the wavelength of the radiation.

FIG. 2B illustrates an exemplary plot 203 of the intensity of lightscattered from a particle (i.e., a nanovoid) as a function of the angleof incident light. In particular, plot 203 includes a y-axis 202 thatrepresents a base-ten logarithm of the relative intensity of thescattered light (such as scattered light 214 of FIG. 2A) to the incidentlight (such as the incident light 210 of FIG. 2A). Further, plot 203includes an x-axis 204 representing the scattering angle in units ofdegrees. Additionally, the angle represented by the x-axis 204 may bemeasured with respect to the incident light. Plot 203 also includes acurve 206 representing a case where the size of the particles (i.e.,average diameter of nanovoids) is about one-fifth the wavelength of theincident light. As shown by curve 206, a relatively large portion of thescattered light may propagate in forward or backward directions withrespect to the particles (e.g., angles in the range of about 0 degreesor about 180 degrees). Comparatively less scattered light may propagatein directions perpendicular to the incident light (e.g., angles in therange of about 90 degrees). In one embodiment, if the switchableelectroactive device is illuminated using a projector (e.g., anultra-short-throw projector) from the an off-axis position (as shown anddescribed in connection with FIGS. 5-8, below), the scattering angle maybe in the range of about 50 degrees to about 80 degrees in order for thelight to propagate into the eyebox of an HMD as described herein.Accordingly, roughly 20% or less of the scattered light may propagateinto the eyebox when the nanovoids have a particle size of aboutone-fifth the wavelength of the incident light.

FIG. 3 shows the relative intensity of scattered light as a function ofparticle size. Again, the particles may correspond to nanovoids in thevarious electroactive elements described herein. Diagram 300 includes ay-axis 302 that represents the base-ten logarithm of the relativeintensity of scattered light from the particles to light incident on theparticles. Further, diagram 300 includes an x-axis 304 that representsthe scattering angle of the light with respect to the particles in unitsof degrees. Moreover, diagram 300 includes curves 306, 308, 310, and 312that represent the sizes of the particles, the sizes varying from aboutλ/20, about λ/10, about λ/5, and about λ, respectively. Diagram 300illustrates that, as the particle size changes by a factor of abouttwenty, the amount of scattered light changes by about eight orders ofmagnitude. Diagram 300 therefore illustrates how the size of thenanovoids in the electroactive elements described herein may beconfigured to provide for optimal light scattering suited to particulardisplay modes in the electroactive devices used in an HMD.

FIG. 4A illustrates an exemplary graphical representation of thefraction of scattered light as a function of density of particles in avolume and as a function of particle size. Diagram 401 includes a y-axis402 that represents the particle size (e.g., nanovoid size) as afraction of the wavelength of incident light in normalized units.Further, diagram 401 includes an x-axis 404 that represents the densityof the nanovoids in units of cubic millimeters. Additionally, diagram401 includes a heat map represented by legend 408 that corresponds tothe base-ten logarithm of the fraction of scattered light from theparticles.

Diagram 401 demonstrates that incident light may be scattered when thedensity of particles increases and as the particle size increases.Moreover, diagram 401 shows that, for certain densities (for exampleabout fifty particles per cubic millimeter), if the particle sizechanges from about 0.1 to about 1 units of wavelength, the amount ofscattered light may change by more than five to six orders of magnitude.For example, arrow 411 indicates that the scattered light intensity maychange as the size and density of the nanovoids changes duringmechanical compression and relaxation of an electroactive element.Accordingly, diagram 400 illustrates how the sizes and/or densities ofthe nanovoids may be configured in the electroactive elements describedherein to provide for optimal scattering suited to particular displaymodes in connection with the electroactive devices.

FIG. 4B illustrates another exemplary graphical representation of thefraction of scattered light as a function of density of particles in avolume and as a function of particle size. Moreover, diagram 403 shows adifferent scale (e.g., a zoomed-in scale) for the y-axis 412 than thatof corresponding y-axis 402 of FIG. 4A. Additionally, two representativepoints have been shown in connection with diagram 403, namely (49.5,0.2, −4.539) and (49.5, 1, −0.345), where the points are represented as(X, Y, Z) tuples, where X represents the density of the particles, Yrepresents the particle size, and Z represents the fraction of scatteredlight from the particles. Accordingly, the points represent differentfractions of scattered light based on different densities and sizes ofnanovoids.

In some embodiments, as described further below, the electroactivedevice may be used as a screen in conjunction with a projector that canproject light at visible or near-visible wavelengths. FIG. 5 is anillustration of an exemplary scenario demonstrating the use of aswitchable display screen for various artificial-reality applications(e.g., virtual-reality, augmented-reality, and/or mixed-realityapplications). As shown in diagram 501, components of an exemplary HMDmay include a projector 504 (e.g., an ultra-short-throw projector) thatis positioned off-axis with respect to an eyepiece 506 and anelectroactive device 508 (e.g., a screen) to project light onto theelectroactive device 508. The eyepiece 506 may be positioned between theeye 502 of a user and the electroactive device 508. In this example, theeyepiece 506 may include at least two states, or modes, of operation. InFIG. 5, the eyepiece 506 may be in an inactive state (or an active statein some examples). The electroactive device 508 may include anelectroactive element in a compressed state (e.g., where theelectroactive element is transparent), similar to the state shown anddescribed in connection with FIG. 1B, above. In the inactive state, theeyepiece 506 may serve as a low power optical element or as an opticalwindow. Further, when the eyepiece 506 is in the inactive state, theelectroactive device 508 may also be in a compressed state where theelectroactive device 508 is transparent or semi-transparent.Accordingly, light 512 may be transmitted through the electroactivedevice 508, allowing for the user's surroundings, which include anobject 510, to be viewed by the user's eye 502.

In some examples, the eyepiece 506 may include any suitable type of lensor combination of lenses, such as a pancake lens, a geometric phaselens, and/or a meta lens. In some examples, the eyepiece 506 may be apancake lens in a predetermined polarization state. The inactive stateof the eyepiece 506 may be used in conjunction with the compressed stateof the electroactive device 508, shown in FIG. 5, to enable the user toview the surrounding environment.

FIG. 6 is an illustration of another exemplary scenario demonstrating aswitchable display screen for virtual-reality and mixed-realityapplications. In particular, diagram 601 of FIG. 6 represents the samecomponents as that of diagram 501 of FIG. 5 shown and described above;however, the electroactive device 608 is in an uncompressed state thatis opaque or substantially opaque (e.g., similar to the uncompressedstate of the electroactive device shown and described in connection withFIG. 1A, above) and is utilized as a screen that is viewable by eye 502.The uncompressed state of the electroactive device 608 may be configured(e.g., via a switching circuitry, not shown) to correspond to theprojection of light 611 (i.e., image light) by the projector 504 ontothe electroactive device. Moreover, the eyepiece 606 may be configured(e.g., via a switching circuitry, not shown) to be in an active state(or an inactive state in some examples) at a time when the electroactivedevice 608 is in the uncompressed state. In the active state, theeyepiece 606 may have a shorterfocal length as compared with theeyepiece 506 in the inactive state shown in FIG. 5, above. Therefore,the eyepiece 606 may focus light 612 from the switchable electroactivedevice 608 in the uncompressed state. Accordingly, the electroactivedevice 608 in the uncompressed state may scatter the light 612 towardsthe user's eye 502, for example, via an eyebox (not shown) of the HMD.The resolution of the system depicted in diagram 601 may be determined,at least in part, by the density of nanovoids in the electroactiveelement in the electroactive device 608.

The active state of the eyepiece 606 may be used in conjunction with theuncompressed state of the electroactive device 608, as shown in FIG. 6,to block or partially obscure the user's view of the externalenvironment for use in a virtual-reality, mixed-reality, and/oraugmented-reality application.

FIG. 7 is an illustration of an exemplary scenario demonstrating aswitchable display screen and eyepieces for virtual-reality,augmented-reality, and/or mixed-reality applications. In particular,diagram 701 of FIG. 7 represents the same components of an HMD as thatof diagram 501 of FIG. 5 shown and described above; however, diagram 701includes an additional eyepiece 714. The eyepiece 706 may be referred toas a proximate eyepiece 706 and the additional eyepiece 714 may bereferred to as a distal eyepiece 714. Moreover, the additional eyepiece714 may be positioned near a surface of the electroactive device 508opposite the proximate eyepiece 706. Additional eyepiece 714 may beconfigured to enable the user to focus on the external environment(e.g., including object 510) without adjusting a state of eyepiece 706,which is also configured to focus image light reflected fromelectroactive device 608 to the user's eye 502 when electroactive device608 is in an uncompressed, opaque state (see FIG. 8).

As depicted in diagram 701, light 512 may propagate from various objectsin the external environment, such as object 510, through the additionaleyepiece 714 and other optical components, including electroactivedevice 508 in a compressed (i.e., transparent) state and eyepiece 706,to travel to the user's eye 502. In such an application as depicted indiagram 701, the projector 504 may be in an off state. In the exemplaryscenario illustrated in diagram 701, the user's eye 502 may view object510 in the real world (e.g., in an augmented-reality application),without interference from the electroactive device 508. In someembodiments, additional eyepiece 714 may allow for the user to view theexternal environment without changing (or minimally changing) the stateof eyepiece 706, allowing the user to focus on both the externalenvironment (e.g., object 510) when electroactive device 508 is in thecompressed state of FIG. 7 and an image displayed on electroactivedevice 608 when electroactive device 608 is in the uncompressed state ofFIG. 8 with little or no adjustment to a state of eyepiece 706 oradditional eyepiece 714. Additionally or alternatively, eyepiece 706and/or additional eyepiece 714 may be adjustable (e.g., a bi-stableeyepiece), allowing for focal adjustments by switching between an activeand an inactive state, as described above in relation to FIGS. 5 and 6.In at least one example, the user's eye 502 may be prescriptivelycorrected by one or more of the eyepiece 706 or the additional eyepiece714.

FIG. 8 shows an illustration of another exemplary scenario demonstratinga switchable display screen and eyepieces for virtual-reality,augmented-reality, and/or mixed-reality applications. In particular,diagram 801 of FIG. 8 represents the same components as that of FIG. 7.However, in diagram 801, the electroactive device 608 is in anuncompressed state that is opaque or substantially opaque (e.g., similarto the state of the electroactive device shown and described inconnection with FIG. 1A, above) and is utilized as a screen that isviewable by eye 502. The disclosed systems may configure (e.g., via aswitching circuitry, not shown) the uncompressed state of theelectroactive device 608 to correspond to the projection of light 611(i.e., image light) by the projector 504 onto the electroactive device608. The eyepiece 706 may focus light 612 from the switchableelectroactive device 608, which is in the uncompressed state.Accordingly, the electroactive device 608 may scatter the light 512towards the user's eye 502, for example, via an eyebox (not shown) ofthe HMD.

In the exemplary scenario depicted in diagram 801, the light 512, whichis blocked and reflected towards the eye 502 by switchable electroactivedevice 608, may not reach, or may be inhibited from reaching, theadditional eyepiece 714. The resolution of the optical system depictedin diagram 801 (or in diagram 601 of FIG. 6, above) may be determined,at least in part, by the density of nanovoids in the electroactiveelement in the electroactive device 608. Further, in augmented-realityapplications, switchable electroactive device 608 (and/or one or moreother components, such as a switchable eyepiece 706 and/or eyepiece 714in some examples) may have a relatively fast switching speed, enablinguse of the HMD in augmented-reality applications. If one or more of thecomponents (e.g., switchable electroactive device 608, and a switchableeyepiece 706 and/or eyepiece 714 in some examples) do not haverelatively fast switching speeds, the system may be used invirtual-reality and/or mixed-reality applications as compared withaugmented-reality applications.

FIG. 9 is an illustration of an exemplary scenario demonstrating aswitchable privacy screen in a compressed state for augmented-realityapplications. In particular, diagram 901 of FIG. 9 includes some of thecomponents also shown in diagram 501 of FIG. 5, as described above, buthas some notable differences. In particular, diagram 501 includes awaveguide display 904 and a switchable electroactive device 908.Further, diagram 900 does not include a projector (e.g., similar toprojector 504 in diagram 501 of FIG. 5) and may not include an eyepiece(e.g., similar to eyepiece 506 in diagram 501). Moreover, as shown indiagram 901, waveguide display 904 may be positioned between the eye 502and the electroactive device 908 and may be configured to transmit light907 (i.e., image light) directly to the eye 502 without the aid ofelectroactive device 908 (i.e., without utilizing electroactive device908 as a screen to reflect light toward eye 502).

Further, light 512 (which may include ambient light, including lightfrom object 510) may propagate through the waveguide display 904, whichmay be at least partially transparent in the state depicted. Thewaveguide display 904 may be configured to operate with a light source(e.g., a microLED, an LED, an OLED, a laser, and/or the like). Diagram901 illustrates that the switchable electroactive device 908 may be in acompressed state where the electroactive device 908 is transparent(e.g., similar to the state shown and described in connection with FIG.1B, above). In the exemplary scenario illustrated in diagram 901, theuser's eye 502 may view object 510 in the real world (e.g., in anaugmented-reality or mixed-reality application), with little or nointerference from the electroactive device 908 or waveguide display 904.

FIG. 10 is an illustration of another exemplary scenario demonstrating aswitchable privacy screen (i.e., electroactive device 1008) in anuncompressed state for augmented-reality applications. In particular,diagram 1001 of FIG. 10 represents some of the components shown anddescribed in connection with diagram 901 of FIG. 9 and diagram 501 ofFIG. 5, above. Diagram 1001 also shows the waveguide display 904.Moreover, diagram 1001 includes switchable electroactive device 1008 inthe uncompressed state. Further, diagram 1001 does not show a projector(e.g., projector 504 as shown in diagram 501). While diagram 1001 doesnot show an eyepiece (e.g., eyepiece 506 in diagram 501), an eyepiecemay additionally be used in some examples to prescriptively correct theuser's eye or to otherwise focus light from waveguide display 904.

As shown in diagram 1001, ambient light (e.g., light 512 shown indiagram 901 of FIG. 9, above) may be blocked by the switchableelectroactive device 1008, which is in an uncompressed state where it isopaque or substantially opaque. This state may be similar to theuncompressed state of the electroactive device shown and described inconnection with FIG. 1A, above.

In the exemplary scenario illustrated in diagram 1001, the user's eye502 may view content displayed as light 907 via the waveguide display904 (e.g., in a virtual-reality application) with little or nointerference from ambient light. Moreover, the system depicted bydiagram 1001 may provide a degree of privacy to the users of the HMD byusing the electroactive device 1008 in an uncompressed opaque state thatprevents content from being viewed by external individuals and devices.

The diagrams of FIGS. 5-10 shown and described above may be used inconnection with a device such as an HMD. In some embodiments, the HMDmay include a near eye display (NED), which may include one or moredisplay devices that may present various media to a user. Examples ofmedia presented by the display device include one or more images, aseries of images (e.g., a video), audio, or some combination thereof. Insome embodiments, audio may be presented via an external device (e.g.,speakers and/or headphones) that receives audio information from thedisplay device, a console (not shown), or both, and presents audio databased on the audio information. The display device may be generallyconfigured to operate as an augmented-reality or mixed-reality NED, suchthat a user may see media projected by the display device and see thereal-world environment through the display device. However, in someembodiments, the display device may be modified to also operate as avirtual-reality NED or some combination of virtual-reality,mixed-reality, and/or augmented-reality NED. Accordingly, in someembodiments, the display device may augment views of a physical,real-world environment with computer-generated elements (e.g., images,video, sound, etc.).

FIG. 11 illustrates an exemplary method for operating an exemplaryswitchable electroactive device as described herein. At block 1102, themethod may include applying an electric field to an electroactiveelement of an electroactive device via electrodes of the electroactivedevice that are electrically coupled to the electroactive element tocompress the electroactive element from an uncompressed state to acompressed state, in accordance with various embodiments as describedherein. In some examples, the electroactive element may include apolymer material defining nanovoids. The electric field may be appliedto the electroactive element such that an average size of the nanovoidsis decreased and a density of the nanovoids is increased in theelectroactive element.

At block 1104, the method may include emitting image light from anemissive device positioned such that at least a portion of the imagelight is incident on a surface of the electroactive device facing theuser's eye, in accordance with various embodiments as described herein.The emissive device may include, for example, at least one of anultra-short throw projector or a waveguide display. According to variousembodiments, the electroactive device may be positioned at a distancefrom a user's eye and may be substantially opaque in the uncompressedstate and transparent in the compressed state. Additionally, a degree ofscattering of incident light by the electroactive element may be based,at least in part, on at least one of the density or the average size ofthe nanovoids. In the uncompressed state of the electroactive element,the nanovoids may have a first average size on an order of a wavelengthof incident light, and in the compressed state of the electroactiveelement, the nanovoids may have a second average size that issubstantially smaller than the wavelength of the incident light.

An eyepiece may be positioned between the user's eye and theelectroactive device and the eyepiece may be configured to modify afocus of the user's eye to a focal plane of the electroactive device inan active state of the eyepiece. In this example, the eyepiece may be aproximate eyepiece and the distal eyepiece may be positioned near asurface of the electroactive device opposite the proximate eyepiece. Insome examples, the active state of the eyepiece may be used in a virtualreality application and an inactive state of the eyepiece may be used inan augmented reality application or a mixed reality application.

As variously described herein, the nanovoided electroactive elements maybe used in electroactive devices. In some embodiments, the nanovoidedelectroactive elements may be used to fabricate switchable screens foraugmented-reality systems that may serve as partially transparentdisplays that mix digital images with the real world. Light rays mayreflect off the electroactive device to be redirected towards a user'seye. In other embodiments, the eye may receive redirected rays from thedigital display (e.g., from a projector or light-emitting diodes).Further, the electroactive device may operate like a partial mirror ordisplay screen that redirects display light and selectively lets lightthrough from the real world depending on the state of the electroactivedevice. In such applications, a high scattering state for the redirectedlight along with a high transmission for ambient light may be desired.The electroactive device may include nanovoided electroactive elementshaving high switching speeds such that, when the electroactive device isswitched on and off at a relatively rapid rate (e.g., an oscillatingelectric field is generated on the nanovoided electroactive element),the nanovoided electroactive element may be transmissive. Moreover, whenthe electroactive device is switched off, the nanovoided electroactiveelement may be in an uncompressed state where the electroactive elementis configured to scatter light via Rayleigh scattering.

Electroactive Devices

In some applications, an electroactive device used in connection withthe principles disclosed herein may include a first electrode, a secondelectrode, and an electroactive element disposed between the firstelectrode and the second electrode. The electroactive element mayinclude an electroactive material such as an electroactive polymer(e.g., a NVP) and a plurality of voids (also referred to herein asnanovoids) distributed within the electroactive polymer, for example asa porous polymer structure. Voids may be generally isolated from eachother, or, at least in part, be interconnected through an open-cellstructure. The plurality of voids may have a non-uniform distributionwithin the electroactive polymer, and the electroactive element may havea non-uniform electroactive response when an electrical signal isapplied between the first electrode and the second electrode, based onthe non-uniform distribution of voids.

A non-uniform distribution of the plurality of voids may include aspatial variation in at least one of void diameter, void volume, voidnumber density, void volume fraction, or void orientation (e.g., in thecase of anisotropic voids). Voids may include a non-polymeric material.Voids may include at least one of a gas, a liquid, a gel, a foam, or anon-polymeric solid. A non-uniform electroactive response may include afirst deformation of a first portion of the electroactive element thatdiffers from a second deformation of a second portion of theelectroactive element. A deformation may include a compression (forexample, parallel to an applied electric field), change in curvature, orother change in a dimensional parameter, such as length, width, height,and the like, in one or more directions. An electroactive device mayhave a first deformation on application of a first voltage between thefirst and second electrodes, and a second deformation on application ofa second voltage between the first and second electrodes, with the firstand second deformations being appreciably different. An electricalsignal may include a potential difference, which may include a direct oralternating voltage. The frequency of alternating voltage may beselected to provide an appreciable haptic sensation on the skin of awearer. In some embodiments, the frequency may be higher than thehighest mechanical response frequency of the device, so that deformationmay occur in response to the applied root-mean-square (RMS) electricfield but with no appreciable oscillatory mechanical response to theapplied frequency. The applied electrical signal may generatenon-uniform constriction of the electroactive element between the firstand second electrodes. A non-uniform electroactive response may includea curvature of a surface of the electroactive element, which may in someembodiments be a compound curvature.

In some embodiments, an electroactive device may include an opticalelement mechanically coupled to the electroactive element. An opticalelement may include at least one of a lens, a grating, a prism, amirror, or a diffraction grating. In some embodiments, the electroactivedevice may be a component of a wearable device. The wearable device mayinclude a helmet or other headwear, an eyewear frame, a glove, a belt,or any device configured to be positioned adjacent to or proximate thebody of a wearer, for example to support the electroactive deviceproximate a user when the user wears the wearable device, and theelectroactive device may be configured to provide a tactile signal tothe user. In some embodiments, an electroactive device includes a firstelectrode, a second electrode, and an electroactive element locatedbetween the first electrode and the second electrode. The electroactiveelement may include an electroactive polymer and a plurality of voidshaving a non-uniform distribution within the electroactive element.Application of a mechanical input to a portion of the electroactiveelement generates an electric signal between the first electrode and thesecond electrode. The electrical response to a mechanical variation mayvary over the electroactive device, with the magnitude being determined,at least in part, by the location of the mechanical input relative tothe non-uniform distribution of voids within the electroactive element.The electroactive element may include a first portion and a secondportion, and a first voltage generated by a mechanical input to thefirst portion is appreciably different from a second voltage generatedby a similar mechanical input to the second portion.

The electroactive device may be a component of a wearable device,configured to be worn by a user. The wearable device may be configuredto support the electroactive device against a body portion of the user.The electroactive device may be configured to provide an electricalsignal correlated with a configuration of the body part, such as aconfiguration of a body part, such as a joint angle. For example, theelectrical signal may be used to determine a joint angle of a fingerportion, wrist, elbow, knee, ankle, toe, or other body joint, or thebend angle of a mechanical device. For example, the wearable device maybe a glove, and the electroactive device may be configured to provide anelectrical signal based, at least in part, on a joint angle within ahand of the user, such as the angle between portions of a finger. Insome embodiments, a method includes generating an electroactive responsein an electroactive device, the electroactive device including anelectroactive element located between a first electrode and a secondelectrode, wherein the electroactive response to an electrical input ora mechanical input varies appreciably over a spatial extent of theelectroactive device due to a non-uniform distribution of voids withinthe electroactive element.

In some embodiments, the electroactive response may include a mechanicalresponse to the electrical input that varies over the spatial extent ofthe electroactive device, with the electrical input being appliedbetween the first electrode and the second electrode. The mechanicalresponse may be termed an actuation, and example devices may be orinclude actuators. In some embodiments, the electroactive response mayinclude an electrical signal having a characteristic indicative of alocation of the mechanical input to the electroactive device, theelectrical signal being measured between the first electrode and thesecond electrode. The electrical signal may be a termed sensor signal,and in some embodiments, the electroactive device may be or include asensor. In some embodiments, an electroactive device may be used as bothan actuator and a sensor. In some embodiments, the electroactive deviceis supported against a hand of a user, and the electrical signal is usedto determine a gesture by the user, the gesture including a fingermovement. In some embodiments, typing inputs by a user, e.g., into avirtual keyboard, may be determined from sensor signals.

In some embodiments, an electroactive device may include one or moreelectroactive elements, and an electroactive element may include one ormore electroactive materials, which may include one or moreelectroactive polymer materials. In various embodiments, anelectroactive device may include a first electrode, a second electrodeoverlapping at least a portion of the first electrode, and anelectroactive element disposed between the first electrode and thesecond electrode. In some embodiments, the electroactive element mayinclude an electroactive polymer. In some embodiments, an electroactiveelement may include an elastomer material, which may be a polymerelastomeric material. In some embodiments, the elastomer material mayhave a Poisson's ratio of approximately 0.35 or less. The electroactiveelement may be deformable from an initial state to a deformed state whena first voltage is applied between the first electrode and the secondelectrode, and may further be deformable to a second deformed state whena second voltage is applied between the first electrode and the secondelectrode.

In some embodiments, there may be one or more additional electrodes, anda common electrode may be electrically coupled to one or more of theadditional electrodes. For example, electrodes and electroactiveelements may be disposed in a stacked configuration, with a first commonelectrode coupled to a first plurality of electrodes, and a secondcommon electrode electrically connected to a second plurality ofelectrodes. The first and second pluralities may alternate in a stackedconfiguration, so that each electroactive element is located between oneof the first plurality of electrodes and one of the second plurality ofelectrodes.

In some embodiments, an electroactive element may have a maximumthickness in an undeformed state and a compressed thickness in adeformed state. In some embodiments, an electroactive element may have adensity in an undeformed state that is approximately 90% or less of adensity of the electroactive element in the deformed state. In someembodiments, an electroactive element may exhibit a strain of at leastapproximately 10% when a voltage is applied between the first electrodeand the second electrode.

In some embodiments, an electroactive element may include at least onenon-polymeric component in a plurality of defined regions and the methodmay further include removing at least a portion of the at least onenon-polymeric component from the cured elastomer material to form ananovoided polymer material.

In some embodiments, an electroactive device may include anelectroactive polymer configured with a first location of patternednanovoids such that the first location has a different transductionbehavior from a second location having a second location of patternednanovoids. In some embodiments, a global electric field applied over theentirety of an electroactive element generates differential deformationbetween the first and second locations. An electroactive element mayhave a plurality of locations of patterned nanovoids such that when afirst voltage is applied the EAP exhibits a predetermined compoundcurvature. The electroactive device may exhibit a second predeterminedcompound curvature, different from the first predetermined compoundcurvature, when a second voltage is applied. A wearable device mayinclude an electroactive device, where the first compound curvatureprovides a first tactile feeling and the second compound curvatureprovides a second tactile feeling to a person when the person is wearingthe wearable device. In some electrodes, the first electrode and/or thesecond electrode may be patterned, allowing a localized electric fieldto be applied to a portion of the device, for example to provide alocalized compound curvature.

In some embodiments, a sensor may include an electroactive device, wherethe electroactive device includes a first and a second portion, wherethe first portion has a different sensor response than the secondportion due to a non-uniform distribution of patterned nanovoids. Thesensor may be a wearable device. The sensor may be in electricalcommunication with a controller configured to determine a flexure of awearable device based on the one or more electrical outputs from thewearable device. For example, the wearable device may include one ormore electroactive devices configured as sensors. In some embodiments, asensor may be configured to determine a joint position of a wearer ofthe sensor based on the one or more electrical signals from the sensor.The sensors may be part of a glove or other wearable device. In someembodiments, the sensor may include an arrangement of electroactivesensors and may be configured to determine keystrokes into a keyboard,where the keyboard may be a real or virtual keyboard.

A non-uniform distribution of voids within an electroactive element mayinclude a functional dependence on a distance parameter, such asdistance from an edge and/or center of an electroactive element. Forexample, an electroactive element may have a generally rectangular shapewith a generally uniform thickness. In some embodiments, the volumefraction of voids may increase monotonically along a direction parallelto a longer side and/or a shorter side of the rectangular shape. In someexamples, the void volume fraction may have a highest value in someportion of the electroactive element and decrease from the highestportion to portions with lower void volume fractions elsewhere, forexample proximate an edge. In some examples, the void volume fractionmay have a lowest value in some portion of the electroactive element andincrease from the lowest portion to portions with higher void volumefractions elsewhere, for example proximate an edge of the electroactiveelement. In some examples, an electroactive element may have a generallydisk shape. The volume fraction of voids may vary as a function of aradial distance from the disk center. In some embodiments, the volumefraction may be highest in a central portion of a disk-shapedelectroactive element and decrease along a radial direction to an edge.In some embodiments, the volume fraction may be lowest in a centralportion and increase along a radial direction to an edge. The variationin void volume fraction may have a functional relationship with adistance parameter, for example including one or more of a linear,quadratic, sinusoidal, undulating, parabolic, or other functionalrelationship with a distance parameter along one or more of the relevantdistance parameters. For example, a distance parameter may be determinedas the distance along an edge, obliquely across, from a center, or otherdistance measurement for a given electroactive element.

An electroactive element can convert deformations into electricalsignals, such as proportional electrical signals that scale with adeformation parameter (such as applied pressure). An electroactiveelement may also receive an electrical signal that induces a deformationbased on the electrical signal (for example, based on the voltagesquared or mean square voltage). An electroactive device may be atransducer, with a degree of deformation based on the electrical signal,and/or as a sensor providing an electrical signal based on a degree ofdeformation. The electroactive response may be mediated by thedielectric constant and elastic modulus of the electroactive element.Using a single homogeneous polymer film constrains the transducerresponse to a particular input electrical signal/output mechanicalresponse across the device. In some embodiments, an electroactive deviceactuates and/or senses deformations as a function of position within asingle device, without the need for complex electrode structures,facilitating electroactive devices (such as transducers and/or sensors)capable of spatially variable actuation and sensing responses, using asimple electrical architecture such as a pair of electrodes.

In some embodiments, a device may include a transducer that convertsvariations in a physical quantity into an electrical signal, and/or viceversa. In some embodiments, the electrical response of a transducer maybe correlated with a location of a mechanical input. The process bywhich variations in a physical quantity transforms into an electricalsignal, and/or vice versa, may be referred to as transduction. Atransducer may include an electroactive element, such an electroactivepolymer element. In some examples, an electroactive element may includean electroactive polymer with a distribution of voids formed therein.

In some embodiments, an electroactive element may include a distributionof voids. In some embodiments, a void may include a region filled with adifferent medium, such as a non-polymeric material, such as a gas suchas air, or a liquid. A portion of the electroactive element may have avolume fraction of voids, which may be determined as the void volumewithin a portion of the electroactive element divided by the totalvolume of the portion of the electroactive element. In some embodiments,the void volume fraction may be a function of a distance parameter. Forexample, the void volume fraction may be a linear function of a distancefrom one edge of an electroactive element, for example increasing in agenerally linear fashion from one side to another. In some examples, thevolume void fraction may be a non-linear function of a distanceparameter, such as a polynomial function (such as a quadratic function),a step function, a parabolic function, an undulating function, a sinefunction, or the like. A distance parameter may be a distance from anedge of an electroactive element. In some embodiments, an electroactiveelement may have a generally cuboid shape, for example having a length,width, and thickness, for example as determined along generally mutuallyorthogonal directions. The thickness of the electroactive element may beapproximately equal to the electrode separation. In some embodiments, anelectroactive element may have a disk shape, a wedge shape, an elongatedform such as a rod, or other shape. A distance parameter may be (asappropriate) a distance along an edge (e.g. a distance from one sidetowards another side), a radial distance (e.g. a distance from a centeror an edge of a disk-shaped form in a generally radial direction), orother distance measurement. In some embodiments, a volume void fractionmay be a function of a distance parameter over a plurality ofelectroactive elements, for example including a plurality ofelectroactive elements having different mean void volume fractions(optionally having an appreciable internal variation of void volumefraction, or in some embodiments no appreciable internal variation ofvoid volume fraction) arranged to obtain a desired variation of voidvolume fraction with distance across a plurality of electroactiveelements.

In some embodiments, a system may include at least one physicalprocessor, a physical memory including computer-executable instructionsthat, when executed by the physical processor, cause the physicalprocessor to apply an electrical field across an electroactive device toobtain non-uniform actuation based on a non-uniform distribution ofvoids within an electroactive element of the electroactive device. Insome embodiments, a system may include at least one physical processor,a physical memory including computer-executable instructions that, whenexecuted by the physical processor, cause the physical processor toreceive an electrical signal from an electroactive device, and toprocess the electrical signal to obtain a deformation parameter of theelectroactive device, wherein the deformation parameter includes one ormore of the following: a magnitude of a deformation, a location of adeformation, a bend angle, a gesture type (e.g., selected from aplurality of gesture types). The analysis of the electrical signal maybe based at least in part on a non-uniform distribution of voids withinan electroactive element of the electroactive device.

Electroactive Elements

In some embodiments, the electroactive elements described herein mayinclude an elastomer having an effective Poisson's ratio of less thanapproximately 0.35 and an effective uncompressed density that is lessthan approximately 90% of the elastomer when densified. In someembodiments, the term “effective Poisson's ratio” may refer to thenegative of the ratio of transverse strain (e.g., strain in a firstdirection) to axial strain (e.g., strain in a second direction) in amaterial. In some embodiments, the electroactive elements may include ananovoided polymer material.

In the presence of an electrostatic field, an electroactive polymer maydeform (e.g., compress, elongates, bend, etc.) according to the strengthof that field. Generation of such a field may be accomplished, forexample, by placing the electroactive polymer between two electrodes,each of which is at a different potential. As the potential difference(i.e., voltage difference) between the electrodes is increased (e.g.,from zero potential) the amount of deformation may also increase,principally along electric field lines. This deformation may achievesaturation when a certain electrostatic field strength has been reached.With no electrostatic field, the electroactive polymer may be in itsrelaxed state undergoing no induced deformation, or stated equivalently,no induced strain, either internal or external.

In some embodiments, a polymer element may include an elastomer. As usedherein, an “elastomer” may (in some examples) refer to a material, suchas a polymer, with viscoelasticity (i.e., both viscosity andelasticity), relatively weak intermolecular forces, and generally lowelastic modulus (a measure of the stiffness of a solid material) andhigh failure strain compared with other materials. In some embodiments,an electroactive polymer may include an elastomer material that has aneffective Poisson's ratio of less than approximately 0.35 (e.g., lessthan approximately 0.3, less than approximately 0.25, less thanapproximately 0.2, less than approximately 0.15, less than approximately0.1, less than approximately 0.05). In at least one example, theelastomer material may have an effective density that is less thanapproximately 90% (e.g., less than approximately 80%, less thanapproximately 70%, less than approximately 60%, less than approximately50%, less than approximately 40%) of the elastomer when densified (e.g.,when the elastomer is compressed, for example, by electrodes to make theelastomer more dense).

In some embodiments, an electroactive element may include an elastomermaterial, which may have a Poisson's ratio of approximately 0.35 orless. In some embodiments, an electroactive element may have a thicknessof approximately 10 nm to approximately 10 μm (e.g., approximately 10nm, approximately 20 nm, approximately 30 nm, approximately 40 nm,approximately 50 nm, approximately 60 nm, approximately 70 nm,approximately 80 nm, approximately 90 nm, approximately 100 nm,approximately 200 nm, approximately 300 nm, approximately 400 nm,approximately 500 nm, approximately 600 nm, approximately 700 nm,approximately 800 nm, approximately 900 nm, approximately 1 μm,approximately 2 μm, approximately 3 μm, approximately 4 μm,approximately 5 μm, approximately 6 μm, approximately 7 μm,approximately 8 μm, approximately 9 μm, approximately 10 μm), with anexample thickness of approximately 200 nm to approximately 500 nm.

An electroactive device may include a plurality of stacked layers; forexample, each layer may include an electroactive element disposedbetween a pair of electrodes. In some embodiments, an electrode may beshared between layers; for example, a device may have alternatingelectrodes and electroactive elements located between neighboring pairsof electrodes. Various stacked configurations can be constructed indifferent geometries that alter the shape, alignment, and spacingbetween layers. Such complex arrangements can enable compression,extension, twisting, and/or bending when operating the electroactivedevice.

Electroactive Polymers

An electroactive element may include one or more electroactive polymersand may also include additional components. As used herein,“electroactive polymers” may (in some examples) refer to polymers thatexhibit a change in size or shape when stimulated by an electric field.Some electroactive polymers may find limited applications due to a lowbreakdown voltage of the polymers with respect to the operating voltageused by electroactive devices (e.g., actuators) that use the polymers.Electroactive devices with reduced operating voltages and higher energydensities may be useful for many applications.

In some embodiments, an electroactive polymer may include a deformablepolymer that may be symmetric with regard to electrical charge (e.g.,polydimethylsiloxane (PDMS), acrylates, etc.) or asymmetric (e.g., poledpolyvinylidene fluoride (PVDF) or its copolymers such aspoly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE)). Additionalexamples of polymer materials forming electroactive polymer materialsmay include, without limitation, styrenes, polyesters, polycarbonates,epoxies, halogenated polymers, such as PVDF, copolymers of PVDF, such asPVDF-TrFE, silicone polymers, and/or any other suitable polymermaterials. Such materials may have any suitable dielectric constant orrelative permittivity, such as, for example, a dielectric constantranging from approximately 2 to approximately 30.

The physical origin of the compressive nature of electroactive polymersin the presence of an electrostatic field (E-field), being the forcecreated between opposite electric charges, is that of the Maxwellstress, which is expressed mathematically with the Maxwell stresstensor. The level of strain or deformation induced by a given E-field isdependent on the square of the E-field strength, the dielectric constantof the electroactive polymer, and on the elastic compliance of thematerial in question. Compliance in this case is the change of strainwith respect to stress or, equivalently, in more practical terms, thechange in displacement with respect to force.

Voids

In some embodiments, the electroactive elements described herein mayinclude voids, such as nanovoids (e.g., having a plurality of voidsand/or nanoscale-sized voids in an electroactive element including anelectroactive polymer or composite thereof). In some embodiments, thenanovoids may occupy at least approximately 10% (e.g., approximately 10%by volume, approximately 20% by volume, approximately 30% by volume,approximately 40% by volume, approximately 50% by volume, approximately60% by volume, approximately 70% by volume, approximately 80% by volume,approximately 90% by volume) of the volume of the electroactiveelements. The voids and/or nanovoids may be either closed- oropen-celled, or a mixture thereof. If they are open-celled, the voidsize may be the minimum average diameter of the cell. In someembodiments, the polymer layer may include a thermoset material and/orany other suitable material having an elastic modulus of less thanapproximately 10 GPa (e.g., approximately 0.5 GPa, approximately 1 GPa,approximately 2 GPa, approximately 3 GPa, approximately 4 GPa,approximately 5 GPa, approximately 6 GPa, approximately 7 GPa,approximately 8 GPa, approximately 9 GPa).

The voids and/or nanovoids may be any suitable size and, in someembodiments, the voids may approach the scale of the thickness of thepolymer layer in the undeformed state. For example, the voids may bebetween approximately 10 nm to about equal to the gap between the pairedtwo electrodes. In some embodiments, the voids may be betweenapproximately 10 nm and approximately 1000 nm, such as betweenapproximately 10 and approximately 200 nm (e.g., approximately 10 nm,approximately 20 nm, approximately 30 nm, approximately 40 nm,approximately 50 nm, approximately 60 nm, approximately 70 nm,approximately 80 nm, approximately 90 nm, approximately 100 nm,approximately 110 nm, approximately 120 nm, approximately 130 nm,approximately 140 nm, approximately 150 nm, approximately 160 nm,approximately 170 nm, approximately 180 nm, approximately 190 nm,approximately 200 nm, approximately 250 nm, approximately 300 nm,approximately 400 nm, approximately 500 nm, approximately 600 nm,approximately 700 nm, approximately 800 nm, approximately 900 nm, and/orapproximately 1000 nm).

In some embodiments, the term “effective density,” as used herein, mayrefer to a parameter that may be obtained using a test method where auniformly thick layer of the elastomer may be placed between two flatand rigid circular plates. In some embodiments, the diameter of theelastomer material being compressed may be at least 100 times thethickness the elastomer material. The diameter of the elastomer materialmay be measured, then the plates may be pressed together to exert apressure of at least approximately 1×106 Pa on the elastomer, and thediameter of the elastomer is remeasured. The effective density may bedetermined from an expression (DR=D_uncompressed/D_compressed), where DRmay represent the effective density ratio, D_uncompressed may representthe density of the uncompressed polymer, and D_compressed may representthe density of the uncompressed polymer.

The density of voids within an electroactive element, or otherdielectric material, may vary as a function of position. In someembodiments, the volume fraction of an electroactive component (ordielectric material) may vary between 10% and 60%. The structure of thevoids may be interconnected (open cell) or the voids may be fullyenclosed by suitable dielectric material (closed cell). The voids may bepartially filled with a dielectric liquid or dielectric gas. The voidsmay be partially coated with a layer of suitable material. In someembodiments, a voided material (such as a porous material) may befabricated using a templating agent, such as a material that directs thestructural formation of pores or other structural elements of anelectroactive element. A templating agent may be any phase of matter(solid, liquid, gas). In some embodiments, a templating agent is removedto produce a pore (or void).

Particles

In some embodiments, the electroactive elements described herein mayinclude particles including a material having a high dielectricconstant, with the particles having an average diameter betweenapproximately 10 nm and approximately 1000 nm. In some embodiments, thematerial having the high dielectric constant may include bariumtitanate.

In some embodiments, an electroactive element may include one or morepolymers, and may additionally include a plurality of particles. In someembodiments, an electroactive element may include particles of amaterial to assist the formation of voids, support voided regions, orboth. Example particle materials include: a silicate, such as silica,including structures resulting from silica gels, fumed silica; atitanate, such as barium titanate; a metal oxide, such as a transitionmetal oxide, such as titanium dioxide; another oxide; composites orcombinations thereof; or other particle material. The particles may havean average diameter between approximately 10 nm and approximately 1000nm, and the particles may form branched or networked particles withaverage dimensions of between approximately 100 and approximately 10,000nm.

In some embodiments, an electroactive element may include particles of amaterial having a high dielectric constant. In some embodiments, theparticles may have an average diameter between approximately 10 nm andapproximately 1000 nm. In some embodiments, the particle material mayhave a high dielectric constant. In some embodiments, the particlematerial may include a titanate, such as barium titanate (BaTiO3), orother perovskite material such as other titanates.

Additionally or alternatively, any other suitable component may be addedto the electroactive polymer material. BaTiO3 is a ferroelectricmaterial with a relatively high dielectric constant (e.g., a value ofbetween approximately 500 and approximately 7000) and polarization andmay be used in various electroactive devices described herein. Besideslarge polarizability and permittivity, large strains may also beachievable with BaTiO3. Pure BaTiO3 is an insulator whereas upon dopingit may transform into a semiconductor in conjunction with the polymermaterial. In some embodiments, the particles of the materials havinghigh dielectric constant may be included in the polymer to modify amechanical (e.g., a Poisson's ratio) or electrical property (resistance,capacitance, etc.) of the first electroactive element or the secondelectroactive element.

In some embodiments, an electroactive device includes a first electrode,a second electrode and a voided polymer layer interposed between atleast a portion of the area of the first and second electrode. In someembodiments, the voided polymer layer has no periodic structure onlength scales greater than 10 nm and the voids have a characteristiclength scale that is less than 1 micron. Voids may form a connectedstructure in an open cell configuration, or the voids may be surrounded,e.g., by dielectric material in a closed cell configuration. In someembodiments, a voided dielectric material may further include particlesof a material with a high dielectric constant, such as a solid such asbarium titanite. In some embodiments, voids may be filled with a fluid,such as a liquid or a gas, for example a dielectric liquid or adielectric gas with high dielectric strength gas, such as a halide, inparticular a fluoride such as is sulfur hexafluoride, organofluoride orthe like.

Electrodes

In some embodiments, an “electrode,” as used herein, may refer to aconductive material, which may be in the form of a film or a layer. Theelectrode may be self-healing, such that when an area of an active layer(e.g., an electroactive element) shorts out, the electrode may be ableto isolate the damaged area.

In some embodiments, the electrodes (e.g., such as a first electrode, asecond electrode, or any other electrode) may include a metal such asaluminum, gold, silver, tin, copper, indium, gallium, zinc, and thelike. An electrode may include one or more electrically conductivematerials, such as a metal, a semiconductor (such as a dopedsemiconductor), carbon nanotube, graphene, transparent conductive oxides(TCOs, e.g., indium tin oxide (ITO), zinc oxide (ZnO), etc.), or otherelectrically conducting material.

In some embodiments, electroactive devices may include pairedelectrodes, which allow the creation of the electrostatic field thatforces constriction of the electroactive polymer. Such electrodes mayinclude relatively thin, electrically conductive layers or elements andmay be of a non-compliant or compliant nature. Any suitable materialsmay be utilized in the electrodes, including electrically conductivematerials suitable for use in thin-film electrodes, such as, forexample, aluminum, transparent conductive oxides, silver, indium,gallium, zinc, carbon nanotubes, carbon black, and/or any other suitablematerials formed by vacuum deposition, spray, adhesion, and/or any othersuitable technique either on a non-electroactive polymer layer ordirectly on the electroactive polymer surface itself. In someembodiments, the electrode or electrode layer may be self-healing, suchthat damage from local shorting of a circuit can be isolated. Suitableself-healing electrodes may include thin films of metals, such as, forexample, aluminum.

In some embodiments, one or more electrodes may be optionallyelectrically interconnected, e.g., through a contact layer, to a commonelectrode. In some embodiments, an electroactive device may have a firstcommon electrode, connected to a first plurality of electrodes, and asecond common electrode, connected to a second plurality of electrodes.In some embodiments, electrodes (e.g., one of a first plurality ofelectrodes and one of a second plurality of electrodes) may beelectrically isolated from each other using an insulator, such as adielectric layer. An insulator may include a material withoutappreciable electrical conductivity, and may include a dielectricmaterial, such as, for example, an acrylate or silicone polymer. In someembodiments, an electrode (or other electrical connector) may include ametal (e.g., tin, aluminum, copper, gold, silver, and the like). In someembodiments, an electrode (such as an electrical contact) or anelectrical connector may include a similar material to other similarcomponents.

In some embodiments, a first electrode may overlap (e.g., overlap in aparallel direction) at least a portion of a second electrode. The firstand second electrode may be generally parallel and spaced apart. A thirdelectrode may overlap at least a portion of either the first or secondelectrode. An electroactive element may include a first polymer (e.g.,an elastomer material) and may be disposed between a first pair ofelectrodes (e.g., the first electrode and the second electrode). Asecond electroactive element, if used, may include a second elastomermaterial and may be disposed between second a pair of electrodes. Insome embodiments, there may be an electrode that is common to both thefirst pair of electrodes and the second pair of electrodes.

In some embodiments, a common electrode may be electrically coupled(e.g., electrically contacted at an interface having a low contactresistance) to one or more other electrode(s), e.g., a second electrodeand a third electrode located either side of a first electrode. In someembodiments, an electroactive device may include additionalelectroactive elements interleaved between electrodes, for example in astacked configuration. For example, electrodes may form aninterdigitated stack of electrodes, with alternate electrodes connectedto a first common electrode and the remaining alternate electrodesconnected to a second common electrode. For example, an additionalelectroactive element may be disposed on the other side of a firstelectrode. The additional electroactive element may overlap a firstelectroactive element. An additional electrode may be disposed abuttinga surface of any additional electroactive element. In some embodiments,an electroactive device may include more (e.g., two, three, or more)such additional electroactive elements and corresponding electrodes. Forexample, an electroactive device may include a stack of two or moreelectroactive elements and corresponding electrodes. For example, anelectroactive device may include between 2 electroactive elements toapproximately 5, approximately 10, approximately 20, approximately 30,approximately 40, approximately 50, approximately 100, approximately200, approximately 300, approximately 400, approximately 500,approximately 600, approximately 700, approximately 800, approximately900, approximately 1000, approximately 2000, or greater thanapproximately 2000 electroactive elements.

In some embodiments, electrodes may be flexible and/or resilient and maystretch, for example elastically, when an electroactive elementundergoes deformation. Electrodes may include one or more transparentconducting oxides (TCOs) such as indium oxide, tin oxide, indium tinoxide (ITO) and the like, graphene, carbon nanotubes, and the like. Inother embodiments, for example, embodiments where electroactive deviceshave electroactive elements including nanovoided electroactive polymermaterials, relatively rigid electrodes (e.g., electrodes including ametal such as aluminum) may be used.

In some embodiments, an electrode (e.g., the first and/or secondelectrode, or any other electrode) may have an electrode thickness ofapproximately 1 nm to approximately 100 nm, with an example thickness ofapproximately 10 nm to approximately 50 nm. In some embodiments, anelectrode may be designed to allow healing of electrical breakdown(e.g., the electric breakdown of elastomeric polymer materials) of anelectroactive element. In some embodiments, an electrode may have anelectrode thickness of approximately 20 nm. In some embodiments, acommon electrode may have a sloped shape, or may be a more complex shape(e.g., patterned or freeform). In some embodiments, a common electrodemay be shaped to allow compression and expansion of an electroactivedevice during operation.

Electrode Fabrication

In some embodiments, the electrodes described herein (e.g., the firstelectrode, the second electrode, or any other electrode including anycommon electrode) may be fabricated using any suitable process. Forexample, electrodes may be fabricated using physical vapor deposition(PVD), chemical vapor deposition (CVD), sputtering, spray-coating,spin-coating, atomic layer deposition (ALD), and the like. In someembodiments, an electrode may be manufactured using a thermalevaporator, a sputtering system, a spray coater, a spin-coater, an ALDunit, and the like. In some embodiments, an electroactive element may bedeposited directly on to an electrode. In some embodiments, an electrodemay be deposited directly on to the electroactive element. In someembodiments, electrodes may be prefabricated and attached to anelectroactive element. In some embodiments, an electrode may bedeposited on a substrate, for example a glass substrate or flexiblepolymer film. In some embodiments, an electroactive element may directlyabut an electrode. In some embodiments, there may be a dielectric layer,such as an insulating layer, between an electroactive element and anelectrode. Any suitable combination of processes may be used.

Lens Assembly and Optical Systems

In some embodiments, the electroactive devices described herein mayinclude or be mechanically coupled to one or more optical elements. Anoptical element may include a lens, mirror, prism, holographic element,beam splitter, optical filter, diffraction grating, a display, or otheroptical element. In some embodiments, an electroactive device, such asan actuator, may include or be mechanically coupled to an adjustablelens. An adjustable lens may include any suitable type of lens withadjustable optical properties (e.g., adjustable optical power/focallength, correcting for wave-front distortion and/or aberrations, etc.),a liquid lens, a gel lens, or other adjustable lens. For example, anadjustable lens may include a deformable exterior layer filled with anoptical medium such as a liquid or a semi-solid material (e.g., a gel, asemi-solid polymer, etc.). An adjustable lens may include one or moresubstantially transparent materials (at wavelengths of application) thatmay deform and/or flow under pressure.

A deformable optical element may include a substantially transparent andelastic material. For example, a deformable optical element may includea natural or synthetic elastomer that returns to a resting state when adeforming force is removed. In some embodiments, a deformable opticalelement may be deformed using an electroactive device generating adirectly-driven force to produce a desired optical power or otheroptical property, e.g., for a lens or other optical element. In someembodiments, actuation forces may be applied around a perimeter of adeformable lens and may be generally uniform or variable around theperimeter of a lens. In some embodiments, electroactive devices may beused to actuate deformable optical elements in optical assemblies (e.g.,lens systems).

In some embodiments, an actuator may include a bender. In someembodiments, the term “bender,” as used herein, may refer, withoutlimitation, to an electrically-driven actuator based on a plate or beamdesign that converts in-plane contraction, via an applied electricfield, into out-of-plane displacement. A bender or bending actuator mayinclude an all-electroactive or composite material stack operated in abimorph, unimorph, or multilayered monolith configuration. In someembodiments, the term “unimorph bender,” as used herein, may refer,without limitation, to a beam or plate having an electroactive layer andan inactive layer, in which displacement results from contraction orexpansion of the electroactive layer. In some embodiments, the term“bimorph bender,” as used herein, may refer, without limitation, to abeam or plate having two electroactive layers, in which displacementresults from expansion or contraction of one layer with alternatecontraction or expansion of the second layer.

In some embodiments, the term “multilayer bender,” as used herein, mayrefer, without limitation, to a multilayer stack of electroactive,electrode, and insulation layers integrated with alternating contractingand expanding electroactive layers into a monolithic bender. Thepiezoelectric layers in multilayer piezoelectric benders may enable highelectric fields (and therefore high force and displacement) to occur atlow voltages. Multilayer benders may include multiple thin piezoceramiclayers, which may require lower voltages to achieve similar internalstress to bimorph and unimorph designs. Charge and voltage control inopen or closed loops may also be implemented in multilayer benders, withsome adjustment. In some embodiments, a control system for a multilayerbender may not require a high voltage power supply.

According to some embodiments, an actuator may be a frame-contoured ringbender and/or may include stacked or overlapping benders. Furthermore,actuator volume may be constrained to an edge region outside an opticalaperture, which may include a perimeter volume of a lens, an opticalelement, an optical sub-assembly, etc. As noted, electroactive device(s)such as an actuator (or a set of actuators) may provide equal or variedforce and displacement at discrete points or along a spatially-defineddistribution at the perimeter of a lens.

In some embodiments, an electroactive device may include one or moredirect-drive benders, that may include an electroactive element that isdisposed between two electrodes. In such examples, methods of forming anelectroactive device may involve forming electrodes and an electroactivepolymer simultaneously (e.g., via coflowing, slot die coating, etc.).

In some embodiment, a lens assembly may include multiple deformableoptical elements (e.g., multiple deformable lenses, such as liquidlenses), where the deformation is provided by one or more electroactivedevices.

Methods of Device Fabrication

Various fabrication methods are discussed herein. Properties of theelectroactive element may be varied across its spatial extent by varyingone or more process parameters, such as wavelength, intensity, substratetemperature, other process temperature, gas pressure, application ofadditional radiation, chemical concentration gradients, chemicalcomposition variations (e.g., to control micelle size), or other processparameter. Non-uniform void size distributions may be obtained byvarying the size of sacrificial regions within an electroactive element.

In some embodiments, the electroactive elements described herein (e.g.,electroactive element 100) may be planarized during the fabrication ofelectroactive devices. Moreover, such planarization may be achievedeither in batch or non-batch processing. In some examples, aplanarization layer (PL) may be formed on a surface of the electroactiveelement. In another embodiment, solvent may be evaporated from thenanovoids electroactive element before the PL is formed. In someexamples, the solvent may be allowed to remain in the nanovoidselectroactive element during the PL formation, as the solvent may helpexclude the PL components from the electroactive element. For example, asolvent may be used that is immiscible with the PL components. In someembodiments, the solvent may be allowed to partially evaporate beforeplanarization. Such partial evaporation of the solvent may induce thepartial collapse of the nanovoids, and result in the formation ofanisotropic nanovoids, such as, for example, disk-shaped nanovoids.Further, the electroactive element may be partially cured before partial(or complete) solvent removal from electroactive element the nanovoids,for example, to achieve partial (or otherwise limited) nanovoidcollapse. In some examples, the PL may be used to lock in somedeformation of the electroactive element, such as deformation due topre-stretching or other physical modifications of the electroactiveelement.

In some embodiments, polymers used for the PL may include, but not belimited to, acrylates, halogenated polymers such as fluoropolymersincluding polyvinylidene difluoride (PVDF, polytetrafluoroethylene),copolymers of PVDF including PVDF:TrFE (poly(polyvinylidenefluoride—trifluoroethylene), other fluorinated polyethylenes, otherfluorinated polymers, other polymers, and/or blends or derivativesthereof. The polymers may include nanoparticles to increase dielectricconstant, such as inorganic particles such as: titanates (includingbarium titanate or barium strontium titanate (BaSrTiO₃); oxides such astitanium dioxide (TiO₂), tantalum oxide (Ta₂O₃), aluminum oxide (Al₂O₃),or cerium oxide (CeO₂); other metal oxides such as other transitionmetal oxides, other non-metal oxides, or other compounds such asPbLaZrTiO₃, PbMgNbO₃ and/or PbTi₃. In some examples, the polymers usedfor the PL may additionally include mixtures of curable monomers withcured polymers.

In various embodiments, the PL may be created using the same polymermixture as used in the generation of the electroactive element.Alternatively, the PL may be created using a different polymer material,for example, a polymer material having a similar elasticity parameter(e.g., Young's modulus) to that of a polymer component of theelectroactive element. Further, adhesion between the PL and theelectroactive element may be improved by matching mechanical and/orthermal properties of the PL to that of the electroactive element (e.g.,a polymer matrix of the electroactive element).

Methods of forming an electroactive device include forming electrodesand electroactive elements sequentially (e.g., via vapor deposition,coating, printing, etc.) or simultaneously (e.g., via co-flowing,coextrusion, slot die coating, etc.). Alternatively, the electroactiveelements may be deposited using initiated chemical vapor deposition(iCVD), where, for example, suitable monomers of the desired polymersmay be used to form the desired coating. In some embodiments, monomers,oligomers, and/or prepolymers for forming the electroactive elements mayoptionally be mixed with a solvent and the solvent may be removed fromthe electroactive element during and/or following curing to formnanovoids within the electroactive element.

A method of fabricating an electroactive device may include depositing acurable material onto a first electrode, curing the deposited curablematerial to form an electroactive element (e.g., including a curedelastomer material) and depositing an electrically conductive materialonto a surface of the electroactive element opposite the first electrodeto form a second electrode. In some embodiments, the cured elastomermaterial may have a Poisson's ratio of approximately 0.35 or less. Insome embodiments, a method may further include depositing an additionalcurable material onto a surface of the second electrode opposite theelectroactive element, curing the deposited additional curable materialto form a second electroactive element including a second curedelastomer material, and depositing an additional electrically conductivematerial onto a surface of the second electroactive element opposite thesecond electrode to form a third electrode.

In some embodiments, a method of fabricating an electroactive elementmay include vaporizing a curable material, or a precursor thereof, wheredepositing the curable material may include depositing the vaporizedcurable material onto the first electrode. In some embodiments, a methodof fabricating an electroactive element may include printing the polymeror precursor thereof (such as a curable material) onto an electrode. Insome embodiments, a method may also include combining a polymerprecursor material with at least one other component to form adeposition mixture. In some embodiments, a method may include combininga curable material with particles of a material having a high dielectricconstant to form a deposition mixture.

According to some embodiments, a method may include positioning acurable material between a first electrically conductive material and asecond electrically conductive material. The positioned curable materialmay be cured to form an electroactive element including a curedelastomer material. In some embodiments, the cured elastomer materialmay have a Poisson's ratio of approximately 0.35 or less. In someembodiments, at least one of the first electrically conductive materialor the second electrically conductive material may include a curableelectrically conductive material, and the method may further includecuring the at least one of the first electrically conductive material orthe second electrically conductive material to form an electrode. Inthis example, curing the at least one of the first electricallyconductive material or the second electrically conductive material mayinclude curing the at least one of the first electrically conductivematerial or the second electrically conductive material during curing ofthe positioned curable material.

In some embodiments, a curable material and at least one of a firstelectrically conductive material or a second electrically conductivematerial may be flowable during positioning of the curable materialbetween the first and second electrodes. A method of fabricating anelectroactive device may further include flowing a curable material andat least one of the first electrically conductive material or the secondelectrically conductive material simultaneously onto a substrate.

In some embodiments, methods for fabricating an electroactive device(e.g., an actuator) may include masks (e.g., shadow masks) to controlthe patterns of deposited materials to form the electroactive device. Insome embodiments, the electroactive device may be fabricated on asurface enclosed by a deposition chamber, which may be evacuated (e.g.,using one or more mechanical vacuum pumps to a predetermined level suchas 10-6 Torr or below). A deposition chamber may include a rigidmaterial (e.g., steel, aluminum, brass, glass, acrylic, and the like). Asurface used for deposition may include a rotating drum. In someembodiments, the rotation may generate centrifugal energy and cause thedeposited material to spread more uniformly over any underlyingsequentially deposited materials (e.g., electrodes, polymer elements,and the like) that are mechanically coupled to the surface. In someembodiments, the surface may be fixed and the deposition and curingsystems may move relative to the surface, or both the surface, thedeposition, and/or curing systems may be moving simultaneously.

In some embodiments, an electroactive device (e.g., an actuator, sensor,or the like) may be fabricated by: providing an electrically conductivelayer (e.g., a first electrode) having a first surface; depositing(e.g., vapor depositing) a polymer (e.g., an electroactive polymer) orpolymer precursor (such as a monomer) onto the electrode; as needed,forming a polymer such as an electroactive polymer from the polymerprecursor (e.g., by curing or a similar process); and depositing anotherelectrically conductive layer (e.g., a second electrode) onto theelectroactive polymer. In some embodiments, the method may furtherinclude repeating one or more of the above to fabricate additionallayers (e.g., second electroactive element, other electrodes,alternating stack of polymer layers and electrodes, and the like. Anelectroactive device may have a stacked configuration.

In some embodiments, an electroactive device may be fabricated by firstdepositing a first electrode, and then depositing a curable material(e.g., a monomer) on the first electrode (e.g., deposited using a vapordeposition process). In some embodiments, an inlet (not shown) to adeposition chamber may open and may input an appropriate monomerinitiator for starting a chemical reaction. In some embodiments,“monomer,” as used herein, may refer to a monomer that forms a givenpolymer (i.e., as part of an electroactive element). In other examples,polymerization of a polymer precursor (such as a monomer) may includeexposure to electromagnetic radiation (e.g., visible, UV, x-ray or gammaradiation), exposure to other radiation (e.g., electron beams,ultrasound), heat, exposure to a chemical species (such as a catalyst,initiator, and the like, some combination thereof, and the like.

Deposited curable material may be cured with a source of radiation(e.g., electromagnetic radiation, such as UV and/or visible light) toform an electroactive element that includes a cured elastomer material,for example by photopolymerization. In some embodiments, a radiationsource may include an energized array of filaments that may generateelectromagnetic radiation, a semiconductor device such as light-emittingdiode (LED) or semiconductor laser, other laser, fluorescence or anoptical harmonic generation source, and the like. A monomer and aninitiator (if used) may react upon exposure to radiation to form anelectroactive element. In some embodiments, radiation may includeradiation having an energy (e.g., intensity and/or photon energy)capable of breaking covalent bonds in a material. Radiation examples mayinclude electrons, electron beams, ions (such as protons, nuclei, andionized atoms), x-rays, gamma rays, ultraviolet visible light, or otherradiation, e.g., having appropriately high energy levels. In someembodiments, the cured elastomer material may include at least onenon-polymeric component in a plurality of defined regions and the methodmay further include removing at least a portion of the at least onenon-polymeric component from the cured elastomer material to form avoided (e.g., nanovoided) polymer element.

An electrically conductive material may then be deposited onto a surfaceof the first electroactive element opposite a first electrode to form asecond electrode. An additional curable material may be deposited onto asurface of the second electrode opposite the electroactive element. Forexample, the deposited additional curable material may be cured to forma second electroactive element, for example including a second curedelastomer material. In some embodiments, an additional electricallyconductive material may be deposited onto a surface of the secondelectroactive element opposite the second electrode to form a thirdelectrode.

In some embodiments, a deposition chamber may have an exhaust portconfigured to open to release at least a portion of the vapor in thechamber during and/or between one or more depositions of the materials(e.g., monomers, oligomers, monomer initiators, conductive materials,etc.). In some embodiments, a deposition chamber may be purged (e.g.,with a gas or the application of a vacuum, or both) to remove a portionof the vapor (e.g., monomers, oligomers, monomer initiators, metalparticles, and any resultant by-products). Thereafter, one or more ofthe previous steps may be repeated (e.g., for a second electroactiveelement, and the like). In this way, individual layers of anelectroactive device may be maintained at high purity levels.

In some embodiments, the deposition of the materials (e.g., monomers,oligomers, monomer initiators, conductive materials, etc.) of theelectroactive device may be performed using a deposition process, suchas chemical vapor deposition (CVD), to be described further below. CVDmay refer to a vacuum deposition method used to produce high-quality,high-performance, solid materials. In CVD, a substrate may be exposed toone or more precursors, which may react and/or decompose on thesubstrate surface to produce the desired deposit (e.g., one or moreelectrodes, electroactive polymers, etc.). Frequently, volatileby-products are also produced, which may be removed by gas flow throughthe chamber.

In some embodiments, an electroactive device may be fabricated using anatmospheric pressure CVD (APCVD) coating formation technique (e.g., CVDat atmospheric pressure). In some embodiments, an electroactive devicemay be fabricated using a low-pressure CVD (LPCVD) process (e.g., CVD atsub-atmospheric pressures). In some embodiments, LPCVD may make use ofreduced pressures that may reduce unwanted gas-phase reactions andimprove the deposited material's uniformity across the substrate. In oneaspect, a fabrication apparatus may apply an ultrahigh vacuum CVD(UHVCVD) process (e.g., CVD at very low pressure, typically belowapproximately 10-6 Pa (equivalently, approximately 10-8 torr)).

In some embodiments, an electroactive device may be fabricated using anaerosol assisted CVD (AACVD) process (e.g., a CVD in which theprecursors are transported to the electroactive device) by means of aliquid/gas aerosol, which may be generated ultrasonically or withelectrospray. In some embodiments, AACVD may be used with non-volatileprecursors. In some embodiments, an electroactive device may befabricated using a direct liquid injection CVD (DLICVD) process (e.g., aCVD in which the precursors are in liquid form, for example, a liquid orsolid dissolved in a solvent). Liquid solutions may be injected in adeposition chamber towards one or more injectors. The precursor vaporsmay then be transported to the electroactive device as in CVD. DLICVDmay be used on liquid or solid precursors, and high growth rates for thedeposited materials may be reached using this technique.

In some embodiments, an electroactive device may be fabricated using ahot wall CVD process (e.g., CVD in which the deposition chamber isheated by an external power source and the electroactive device isheated by radiation from the heated wall of the deposition chamber). Inanother aspect, an electroactive device may be fabricated using a coldwall CVD process (e.g., a CVD in which only the electroactive device isdirectly heated, for example, by induction, while the walls of thechamber are maintained at room temperature).

In some embodiments, an electroactive device may be fabricated using amicrowave plasma-assisted CVD (MPCVD) process, where microwaves are usedto enhance chemical reaction rates of the precursors. In another aspect,an electroactive device may be fabricated using a plasma-enhanced CVD(PECVD) process (e.g., CVD that uses plasma to enhance chemical reactionrates of the precursors). In some embodiments, PECVD processing mayallow deposition of materials at lower temperatures, which may be usefulin withstanding damage to the electroactive device or in depositingcertain materials (e.g., organic materials and/or some polymers).

In some embodiments, an electroactive device may be fabricated using aremote plasma-enhanced CVD (RPECVD) process. In some embodiments, RPECVDmay be similar to PECVD except that the electroactive device may not bedirectly in the plasma discharge region. In some embodiments, theremoval of the electroactive device from the plasma region may allow forthe reduction of processing temperatures down to room temperature.

In some embodiments, an electroactive device may be fabricated using anatomic-layer CVD (ALCVD) process. In some embodiments, ALCVD may depositsuccessive layers of different substances to produce layered,crystalline film coatings on the electroactive device.

In some embodiments, an electroactive device may be fabricated using acombustion chemical vapor deposition (CCVD) process. In someembodiments, CCVD (also referred to as flame pyrolysis) may refer to anopen-atmosphere, flame-based technique for depositing high-quality thinfilms (e.g., layers of material ranging from fractions of a nanometer(monolayer) to several micrometers in thickness) and nanomaterials,which may be used in forming the electroactive device.

In some embodiments, an electroactive device may be fabricated using ahot filament CVD (HFCVD) process, which may also be referred to ascatalytic CVD (cat-CVD) or initiated CVD (iCVD). In some embodiments,this process may use a hot filament to chemically decompose the sourcegases to form the materials of the electroactive device. Moreover, thefilament temperature and temperature of portions of the electroactivedevice may be independently controlled, allowing colder temperatures forbetter adsorption rates at the electroactive device, and highertemperatures necessary for decomposition of precursors to free radicalsat the filament.

In some embodiments, an electroactive device may be fabricated using ahybrid physical-chemical vapor deposition (HPCVD) process. HPCVD mayinvolve both chemical decomposition of precursor gas and vaporization ofa solid source to form the materials on the electroactive device.

In some embodiments, an electroactive device may be fabricated usingmetalorganic chemical vapor deposition (MOCVD) process (e.g., a CVD thatuses metalorganic precursors) to form materials on the electroactivedevice. For example, an electrode may be formed on an electroactiveelement using this approach.

In some embodiments, an electroactive device may be fabricated using arapid thermal CVD (RTCVD) process. This CVD process uses heating lampsor other methods to rapidly heat the electroactive device. Heating onlythe electroactive device rather than the precursors or chamber walls mayreduce unwanted gas-phase reactions that may lead to particle formationin the electroactive device.

In some embodiments, an electroactive device may be fabricated using aphoto-initiated CVD (PICVD) process. This process may use UV light tostimulate chemical reactions in the precursor materials used to make thematerials for the electroactive device. Under certain conditions, PICVDmay be operated at or near atmospheric pressure.

In some embodiments, electroactive devices may be fabricated bynanovoided a process including depositing a curable material (e.g., amonomer such as an acrylate or a silicone) and a solvent for the curablematerial onto a substrate, heating the curable material with at least aportion of the solvent remaining with the cured monomer, and removingthe solvent from the cured monomer. Using this process, voids such asnanovoids may be formed in the electroactive element. In someembodiments, a flowable material (e.g., a solvent) may be combined withthe curable materials (e.g., monomers and conductive materials) tocreate a flowable mixture that may be used for producing electroactivepolymers with nanovoids. The monomers may be monofunctional orpolyfunctional, or mixtures thereof. Polyfunctional monomers may be usedas crosslinking agents to add rigidity or to form elastomers.Polyfunctional monomers may include difunctional materials such asbisphenol fluorene (EO) diacrylate, trifunctional materials such astrimethylolpropane triacrylate (TMPTA), and/or higher functionalmaterials. Other types of monomers may be used, including, for example,isocyanates, and these may be mixed with monomers with different curingmechanisms.

In some embodiments, the flowable material may be combined (e.g., mixed)with a curable material (e.g., a monomer). In some embodiments, acurable material may be combined with at least one non-curable component(e.g., particles of a material having a high dielectric constant) toform a mixture including the curable material and the at least onenon-curable component, for example, on an electrode (e.g., a firstelectrode or a second electrode) of the electroactive device.Alternatively, the flowable material (e.g., solvent) may be introducedinto a vaporizer to deposit (e.g., via vaporization or, in alternativeembodiments, via printing) a curable material onto an electrode. In someembodiments, a flowable material (e.g., solvent) may be deposited as aseparate layer either on top or below a curable material (e.g., amonomer) and the solvent and curable material may be allowed to diffuseinto each other before being cured by the source of radiation togenerate an electroactive polymer having nanovoids. In some embodiments,after the curable material is cured, the solvent may be allowed toevaporate before another electroactive polymer or another electrode isformed. In some embodiments, the evaporation of the solvent may beaccelerated by the application of heat to the surface with a heater,which may, for example, by disposed within a drum forming surface and/orany other suitable location, or by reducing the pressure of the solventabove the substrate using a cold trap (e.g., a device that condensesvapors into a liquid or solid), or a combination thereof. Isolators (notshown) may be added to the apparatus to prevent, for example, thesolvent vapor from interfering with the radiation source or theelectrode source.

In some embodiments, the solvent may have a vapor pressure that issimilar to at least one of the monomers being evaporated. The solventmay dissolve both the monomer and the generated electroactive polymer,or the solvent may dissolve only the monomer. Alternatively, the solventmay have low solubility for the monomer, or plurality of monomers ifthere is a mixture of monomers being applied. Furthermore, the solventmay be immiscible with at least one of the monomers and may at leastpartially phase separate when condensed on the substrate.

In some embodiments, there may be multiple vaporizers, with each of themultiple vaporizers applying a different material, including solvents,non-solvents, monomers, and/or ceramic precursors such as tetraethylorthosilicate and water, and optionally a catalyst for forming a sol-gelsuch as HCl or ammonia.

In some embodiments, a method of generating a nanovoided polymer for usein connection with an electroactive device (such as electroactivedevices described variously herein) may include co-depositing a monomeror mixture of monomers, a surfactant, and a nonsolvent materialassociated with the monomer(s) which is compatible with the surfactant.In various examples, the monomer(s) may include, but not be limited to,ethyl acrylate, butyl acrylate, octyl acrylate, ethoxy ethyl acrylate,2-chloroethyl vinyl ether, chloromethyl acrylate, methacrylic acid,allyl glycidyl ether, and/or N-methylol acrylamide. Other curing agentssuch as polyamines, higher fatty acids or their esters, and/or sulfurmay be used as the monomer(s). In some aspects, the surfactant may beionic or non-ionic (for example SPAN 80, available from Sigma-AldrichCompany). In another aspect, the non-solvent material may includeorganic and/or inorganic non-solvent materials. For instance, thenon-solvent material may include water or a hydrocarbon or may include ahighly polar organic compound such as ethylene glycol. As noted, themonomer or monomers, non-solvent, and surfactant may be co-deposited.Alternatively, the monomer or monomers, non-solvent, and/or surfactantmay be deposited sequentially. In one aspect, a substrate temperaturemay be controlled to generate and control one or more properties of theresulting emulsion generated by co-depositing or sequentially depositingthe monomer or monomers, non-solvent, and surfactant. The substrate maybe treated to prevent destabilization of the emulsion. For example, analuminum layer may be coated with a thin polymer layer made bydepositing a monomer followed by curing the monomer.

As discussed throughout the instant disclosure, the disclosed devices,systems, and methods may provide one or more advantages overconventional devices, systems, and methods. For example, in contrast toprior devices, the electroactive devices presented herein may includeelectroactive elements that achieve substantially uniform strain in thepresence of an electrostatic field produced by a potential differencebetween paired electrodes, permitting the electroactive devices toachieve, for example, improvements in both energy density and specificpower density. Such uniform strain may reduce or eliminate unwanteddeformations in the electroactive elements and may result in greateroverall deformation, such as compression, of the electroactive elements,providing a greater degree of movement of surface regions of theelectroactive elements while requiring a lower amount of energy toprovide such deformation. The electroactive elements may include polymermaterials having nanovoided regions that allow for additionalcompression in the presence of a voltage gradient in comparison tonon-voided materials. Additionally, an electroactive device may beformed in a stacked structure having a plurality of electroactiveelements that are layered with multiple electrodes, enabling theplurality of electroactive elements to be actuated in conjunction witheach other in a single device that may undergo a more substantial degreeof deformation (e.g., compression and/or expansion) in comparison to anelectroactive device having a single electroactive element or layer.

Electroactive devices described and shown herein may be utilized in anysuitable technologies, without limitation. For example, suchelectroactive devices may be utilized as mechanical actuators to actuatemovement of adjacent components. In at least one embodiment, thedisclosed electroactive devices may be incorporated into optical systemssuch as adjustable lenses (e.g., fluid-filled lenses) to actuatemovement of one or more optical layers. Such actuation may, for example,allow for selected movement of lens layers of an adjustable lens,resulting in deformation of the lens layers to adjust opticalcharacteristics (e.g., focal point, spherical correction, cylindricalcorrection, axial correction, etc.) of the adjustable lens. In someembodiments, electroactive devices as disclosed herein may be utilizedas actuators in micromechanical apparatuses, such asmicroelectromechanical devices. Additionally or alternatively,electroactive devices may be used for converting mechanical energy toelectrical energy for use in energy harvesting systems and/or sensorapparatuses.

Embodiments of the instant disclosure may include or be implemented inconjunction with various types of artificial reality systems. Artificialreality is a form of reality that has been adjusted in some mannerbefore presentation to a user, which may include, e.g., a virtualreality, an augmented reality, a mixed reality, a hybrid reality, orsome combination and/or derivative thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to, e.g., createcontent in an artificial reality and/or are otherwise used in (e.g., toperform activities in) an artificial reality.

Artificial reality systems may be implemented in a variety of differentform factors and configurations. Some artificial reality systems may bedesigned to work without near-eye displays (NEDs), an example of whichis augmented-reality system 1200 in FIG. 12. Other artificial realitysystems may include a NED that also provides visibility into the realworld (e.g., augmented-reality system 1300 in FIG. 13) or that visuallyimmerses a user in an artificial reality (e.g., virtual-reality system1400 in FIG. 14). While some artificial reality devices may beself-contained systems, other artificial reality devices may communicateand/or coordinate with external devices to provide an artificial realityexperience to a user. Examples of such external devices include handheldcontrollers, mobile devices, desktop computers, devices worn by a user,devices worn by one or more other users, and/or any other suitableexternal system.

Turning to FIG. 12, augmented-reality system 1200 generally represents awearable device dimensioned to fit about a body part (e.g., a head) of auser. As shown in FIG. 12, system 1200 may include a frame 1202 and acamera assembly 1204 that is coupled to frame 1202 and configured togather information about a local environment by observing the localenvironment. Augmented-reality system 1200 may also include one or moreaudio devices, such as output audio transducers 1208(A) and 1208(B) andinput audio transducers 1210. Output audio transducers 1208(A) and1208(B) may provide audio feedback and/or content to a user, and inputaudio transducers 1210 may capture audio in a user's environment.

As shown, augmented-reality system 1200 may not necessarily include aNED positioned in front of a user's eyes. Augmented-reality systemswithout NEDs may take a variety of forms, such as head bands, hats, hairbands, belts, watches, wrist bands, ankle bands, rings, neckbands,necklaces, chest bands, eyewear frames, and/or any other suitable typeor form of apparatus. While augmented-reality system 1200 may notinclude a NED, augmented-reality system 1200 may include other types ofscreens or visual feedback devices (e.g., a display screen integratedinto a side of frame 1202).

The embodiments discussed in this disclosure may also be implemented inaugmented-reality systems that include one or more NEDs. For example, asshown in FIG. 13, augmented-reality system 1300 may include an eyeweardevice 1302 with a frame 1310 configured to hold a left display device1315(A) and a right display device 1315(B) in front of a user's eyes.Display devices 1315(A) and 1315(B) may act together or independently topresent an image or series of images to a user. While augmented-realitysystem 1300 includes two displays, embodiments of this disclosure may beimplemented in augmented-reality systems with a single NED or more thantwo NEDs.

In some embodiments, augmented-reality system 1300 may include one ormore sensors, such as sensor 1340. Sensor 1340 may generate measurementsignals in response to motion of augmented-reality system 1300 and maybe located on substantially any portion of frame 1310. Sensor 1340 mayinclude a position sensor, an inertial measurement unit (IMU), a depthcamera assembly, or any combination thereof. In some embodiments,augmented-reality system 1300 may or may not include sensor 1340 or mayinclude more than one sensor. In embodiments in which sensor 1340includes an IMU, the IMU may generate calibration data based onmeasurement signals from sensor 1340. Examples of sensor 1340 mayinclude, without limitation, accelerometers, gyroscopes, magnetometers,other suitable types of sensors that detect motion, sensors used forerror correction of the IMU, or some combination thereof.

AR system 1300 may also include a microphone array with a plurality ofacoustic sensors 1320(A)-1320(J), referred to collectively as acousticsensors 1320. Acoustic sensors 1320 may be transducers that detect airpressure variations induced by sound waves. Each acoustic sensor 1320may be configured to detect sound and convert the detected sound into anelectronic format (e.g., an analog or digital format). The microphonearray in FIG. 13 may include, for example, ten acoustic sensors: 1320(A)and 1320(B), which may be designed to be placed inside a correspondingear of the user, acoustic sensors 1320(C), 1320(D), 1320(E), 1320(F),1320(G), and 1320(H), which may be positioned at various locations onframe 1310, and/or acoustic sensors 1320(I) and 1320(J), which may bepositioned on a corresponding neckband 1305.

The configuration of acoustic sensors 1320 of the microphone array mayvary. While augmented-reality system 1300 is shown in FIG. 13 as havingten acoustic sensors 1320, the number of acoustic sensors 1320 may begreater or less than ten. In some embodiments, using higher numbers ofacoustic sensors 1320 may increase the amount of audio informationcollected and/or the sensitivity and accuracy of the audio information.In contrast, using a lower number of acoustic sensors 1320 may decreasethe computing power required by the controller 1350 to process thecollected audio information. In addition, the position of each acousticsensor 1320 of the microphone array may vary. For example, the positionof an acoustic sensor 1320 may include a defined position on the user, adefined coordinate on the frame 1310, an orientation associated witheach acoustic sensor, or some combination thereof.

Acoustic sensors 1320(A) and 1320(B) may be positioned on differentparts of the user's ear, such as behind the pinna or within the auricleor fossa. Or, there may be additional acoustic sensors on or surroundingthe ear in addition to acoustic sensors 1320 inside the ear canal.Having an acoustic sensor positioned next to an ear canal of a user mayenable the microphone array to collect information on how sounds arriveat the ear canal. By positioning at least two of acoustic sensors 1320on either side of a user's head (e.g., as binaural microphones),augmented-reality device 1300 may simulate binaural hearing and capturea 3D stereo sound field around about a user's head. In some embodiments,acoustic sensors 1320(A) and 1320(B) may be connected toaugmented-reality system 1300 via a wired connection, and in otherembodiments, the acoustic sensors 1320(A) and 1320(B) may be connectedto augmented-reality system 1300 via a wireless connection (e.g., aBluetooth connection). In still other embodiments, acoustic sensors1320(A) and 1320(B) may not be used at all in conjunction withaugmented-reality system 1300.

Acoustic sensors 1320 on frame 1310 may be positioned along the lengthof the temples, across the bridge, above or below display devices1315(A) and 1315(B), or some combination thereof. Acoustic sensors 1320may be oriented such that the microphone array is able to detect soundsin a wide range of directions surrounding the user wearing theaugmented-reality system 1300. In some embodiments, an optimizationprocess may be performed during manufacturing of augmented-realitysystem 1300 to determine relative positioning of each acoustic sensor1320 in the microphone array.

AR system 1300 may further include or be connected to an external device(e.g., a paired device), such as neckband 1305. As shown, neckband 1305may be coupled to eyewear device 1302 via one or more connectors 1330.Connectors 1330 may be wired or wireless connectors and may includeelectrical and/or non-electrical (e.g., structural) components. In somecases, eyewear device 1302 and neckband 1305 may operate independentlywithout any wired or wireless connection between them. While FIG. 13illustrates the components of eyewear device 1302 and neckband 1305 inexample locations on eyewear device 1302 and neckband 1305, thecomponents may be located elsewhere and/or distributed differently oneyewear device 1302 and/or neckband 1305. In some embodiments, thecomponents of eyewear device 1302 and neckband 1305 may be located onone or more additional peripheral devices paired with eyewear device1302, neckband 1305, or some combination thereof. Furthermore, neckband1305 generally represents any type or form of paired device. Thus, thefollowing discussion of neckband 1305 may also apply to various otherpaired devices, such as smart watches, smart phones, wrist bands, otherwearable devices, handheld controllers, tablet computers, laptopcomputers, etc.

Pairing external devices, such as neckband 1305, with augmented-realityeyewear devices may enable the eyewear devices to achieve the formfactor of a pair of glasses while still providing sufficient battery andcomputation power for expanded capabilities. Some or all of the batterypower, computational resources, and/or additional features ofaugmented-reality system 1300 may be provided by a paired device orshared between a paired device and an eyewear device, thus reducing theweight, heat profile, and form factor of the eyewear device overallwhile still retaining desired functionality. For example, neckband 1305may allow components that would otherwise be included on an eyeweardevice to be included in neckband 1305 since users may tolerate aheavier weight load on their shoulders than they would tolerate on theirheads. Neckband 1305 may also have a larger surface area over which todiffuse and disperse heat to the ambient environment. Thus, neckband1305 may allow for greater battery and computation capacity than mightotherwise have been possible on a stand-alone eyewear device. Sinceweight carried in neckband 1305 may be less invasive to a user thanweight carried in eyewear device 1302, a user may tolerate wearing alighter eyewear device and carrying or wearing the paired device forgreater lengths of time than a user would tolerate wearing a heavystandalone eyewear device, thereby enabling an artificial realityenvironment to be incorporated more fully into a user's day-to-dayactivities.

Neckband 1305 may be communicatively coupled with eyewear device 1302and/or to other devices. The other devices may provide certain functions(e.g., tracking, localizing, depth mapping, processing, storage, etc.)to augmented-reality system 1300. In the embodiment of FIG. 13, neckband1305 may include two acoustic sensors (e.g., 1320(I) and 1320(J)) thatare part of the microphone array (or potentially form their ownmicrophone subarray). Neckband 1305 may also include a controller 1325and a power source 1335.

Acoustic sensors 1320(I) and 1320(J) of neckband 1305 may be configuredto detect sound and convert the detected sound into an electronic format(analog or digital). In the embodiment of FIG. 13, acoustic sensors1320(I) and 1320(J) may be positioned on neckband 1305, therebyincreasing the distance between the neckband acoustic sensors 1320(I)and 1320(J) and other acoustic sensors 1320 positioned on eyewear device1302. In some cases, increasing the distance between acoustic sensors1320 of the microphone array may improve the accuracy of beamformingperformed via the microphone array. For example, if a sound is detectedby acoustic sensors 1320(C) and 1320(D) and the distance betweenacoustic sensors 1320(C) and 1320(D) is greater than, e.g., the distancebetween acoustic sensors 1320(D) and 1320(E), the determined sourcelocation of the detected sound may be more accurate than if the soundhad been detected by acoustic sensors 1320(D) and 1320(E).

Controller 1325 of neckband 1305 may process information generated bythe sensors on neckband 1305 and/or augmented-reality system 1300. Forexample, controller 1325 may process information from the microphonearray that describes sounds detected by the microphone array. For eachdetected sound, controller 1325 may perform a DoA estimation to estimatea direction from which the detected sound arrived at the microphonearray. As the microphone array detects sounds, controller 1325 maypopulate an audio data set with the information. In embodiments in whichaugmented-reality system 1300 includes an inertial measurement unit,controller 1325 may compute all inertial and spatial calculations fromthe IMU located on eyewear device 1302. Connector 1330 may conveyinformation between augmented-reality system 1300 and neckband 1305 andbetween augmented-reality system 1300 and controller 1325. Theinformation may be in the form of optical data, electrical data,wireless data, or any other transmittable data form. Moving theprocessing of information generated by augmented-reality system 1300 toneckband 1305 may reduce weight and heat in eyewear device 1302, makingit more comfortable to the user.

Power source 1335 in neckband 1305 may provide power to eyewear device1302 and/or to neckband 1305. Power source 1335 may include, withoutlimitation, lithium ion batteries, lithium-polymer batteries, primarylithium batteries, alkaline batteries, or any other form of powerstorage. In some cases, power source 1335 may be a wired power source.Including power source 1335 on neckband 1305 instead of on eyeweardevice 1302 may help better distribute the weight and heat generated bypower source 1335.

As noted, some artificial reality systems may, instead of blending anartificial reality with actual reality, substantially replace one ormore of a user's sensory perceptions of the real world with a virtualexperience. One example of this type of system is a head-worn displaysystem, such as virtual-reality system 1400 in FIG. 14, that mostly orcompletely covers a user's field of view. Virtual-reality system 1400may include a front rigid body 1402 and a band 1404 shaped to fit arounda user's head. Virtual-reality system 1400 may also include output audiotransducers 1406(A) and 1406(B). Furthermore, while not shown in FIG.14, front rigid body 1402 may include one or more electronic elements,including one or more electronic displays, one or more inertialmeasurement units (IMUs), one or more tracking emitters or detectors,and/or any other suitable device or system for creating an artificialreality experience.

Artificial reality systems may include a variety of types of visualfeedback mechanisms. For example, display devices in augmented-realitysystem 1300 and/or virtual-reality system 1400 may include one or moreliquid crystal displays (LCDs), light emitting diode (LED) displays,organic LED (OLED) displays, and/or any other suitable type of displayscreen. Artificial reality systems may include a single display screenfor both eyes or may provide a display screen for each eye, which mayallow for additional flexibility for varifocal adjustments or forcorrecting a user's refractive error. Some artificial reality systemsmay also include optical subsystems having one or more lenses (e.g.,conventional concave or convex lenses, Fresnel lenses, adjustable liquidlenses, etc.) through which a user may view a display screen.

In addition to or instead of using display screens, some artificialreality systems may include one or more projection systems. For example,display devices in augmented-reality system 1300 and/or virtual-realitysystem 1400 may include micro-LED projectors that project light (using,e.g., a waveguide) into display devices, such as clear combiner lensesthat allow ambient light to pass through. The display devices mayrefract the projected light toward a user's pupil and may enable a userto simultaneously view both artificial reality content and the realworld. Artificial reality systems may also be configured with any othersuitable type or form of image projection system.

Artificial reality systems may also include various types of computervision components and subsystems. For example, augmented-reality system1200, augmented-reality system 1300, and/or virtual system 1400 mayinclude one or more optical sensors such as two-dimensional (2D) orthree-dimensional (3D) cameras, time-of-flight depth sensors,single-beam or sweeping laser rangefinders, 3D LiDAR sensors, and/or anyother suitable type or form of optical sensor. An artificial realitysystem may process data from one or more of these sensors to identify alocation of a user, to map the real world, to provide a user withcontext about real-world surroundings, and/or to perform a variety ofother functions.

Artificial reality systems may also include one or more input and/oroutput audio transducers. In the examples shown in FIGS. 12 and 14,output audio transducers 1208(A), 1208(B), 1406(A), and 1406(B) mayinclude voice coil speakers, ribbon speakers, electrostatic speakers,piezoelectric speakers, bone conduction transducers, cartilageconduction transducers, and/or any other suitable type or form of audiotransducer. Similarly, input audio transducers 1210 may includecondenser microphones, dynamic microphones, ribbon microphones, and/orany other type or form of input transducer. In some embodiments, asingle transducer may be used for both audio input and audio output.

While not shown in FIGS. 12-14, artificial reality systems may includetactile (i.e., haptic) feedback systems, which may be incorporated intoheadwear, gloves, body suits, handheld controllers, environmentaldevices (e.g., chairs, floormats, etc.), and/or any other type of deviceor system. Haptic feedback systems may provide various types ofcutaneous feedback, including vibration, force, traction, texture,and/or temperature. Haptic feedback systems may also provide varioustypes of kinesthetic feedback, such as motion and compliance. Hapticfeedback may be implemented using motors, piezoelectric actuators,fluidic systems, and/or a variety of other types of feedback mechanisms.Haptic feedback systems may be implemented independent of otherartificial reality devices, within other artificial reality devices,and/or in conjunction with other artificial reality devices.

By providing haptic sensations, audible content, and/or visual content,artificial reality systems may create an entire virtual experience orenhance a user's real-world experience in a variety of contexts andenvironments. For instance, artificial reality systems may assist orextend a user's perception, memory, or cognition within a particularenvironment. Some systems may enhance a user's interactions with otherpeople in the real world or may enable more immersive interactions withother people in a virtual world. Artificial reality systems may also beused for educational purposes (e.g., for teaching or training inschools, hospitals, government organizations, military organizations,business enterprises, etc.), entertainment purposes (e.g., for playingvideo games, listening to music, watching video content, etc.), and/orfor accessibility purposes (e.g., as hearing aids, visuals aids, etc.).The embodiments disclosed herein may enable or enhance a user'sartificial reality experience in one or more of these contexts andenvironments and/or in other contexts and environments.

The process parameters and sequence of the steps described and/orillustrated herein are given by way of example only and can be varied asdesired. For example, while the steps illustrated and/or describedherein may be shown or discussed in a particular order, these steps donot necessarily need to be performed in the order illustrated ordiscussed. The various exemplary methods described and/or illustratedherein may also omit one or more of the steps described or illustratedherein or include additional steps in addition to those disclosed.

The preceding description has been provided to enable others skilled inthe art to best utilize various aspects of the exemplary embodimentsdisclosed herein. This exemplary description is not intended to beexhaustive or to be limited to any precise form disclosed. Manymodifications and variations are possible without departing from thespirit and scope of the instant disclosure. The embodiments disclosedherein should be considered in all respects illustrative and notrestrictive. Reference should be made to the appended claims and theirequivalents in determining the scope of the instant disclosure.

Unless otherwise noted, the terms “connected to” and “coupled to” (andtheir derivatives), as used in the specification and claims, are to beconstrued as permitting both direct and indirect (i.e., via otherelements or components) connection. In addition, the terms “a” or “an,”as used in the specification and claims, are to be construed as meaning“at least one of.” Finally, for ease of use, the terms “including” and“having” (and their derivatives), as used in the specification andclaims, are interchangeable with and have the same meaning as the word“comprising.”

What is claimed is:
 1. A display device, comprising: an electroactivedevice positioned to be located at a distance from a user's eye when thedisplay device is worn by the user, the electroactive device comprising:an electroactive element comprising a polymer material definingnanovoids; and electrodes electrically coupled to the electroactiveelement and configured to apply an electric field to the electroactiveelement, wherein the electroactive element is compressible from anuncompressed state to a compressed state by the application of theelectric field so as to decrease an average size of the nanovoids andincrease a density of the nanovoids in the compressed state, a magnitudeof the electric field associated with a desired size and a desireddensity of the nanovoids between the compressed and uncompressed states;and an emissive device positioned to radiate image light onto anexternal surface of the electroactive device facing the user's eye suchthat the external surface of the electroactive device reflects imagelight toward the user's eye when the electroactive element is in theuncompressed state.
 2. The display device of claim 1, wherein: theelectroactive device is substantially opaque in the uncompressed state;and the electroactive device is transparent in the compressed state. 3.The display device of claim 1, wherein: in the uncompressed state of theelectroactive element, the nanovoids have a first average size on anorder of a wavelength of incident light; and in the compressed state ofthe electroactive element, the nanovoids have a second average size thatis substantially smaller than the wavelength of the incident light. 4.The display device of claim 1, further comprising an eyepiece positionedbetween the user's eye and the electroactive device, the eyepiececonfigured to modify a focus of the user's eye to a focal plane of theelectroactive device in an active state of the eyepiece.
 5. The displaydevice of claim 4, wherein: the active state of the eyepiece is used ina virtual reality application; and an inactive state of the eyepiece isused in an augmented reality application or a mixed reality application.6. The display device of claim 4, wherein: the eyepiece is a proximateeyepiece; and the display device further comprises a distal eyepiecepositioned near a surface of the electroactive device opposite theproximate eyepiece.
 7. The display device of claim 1, wherein theemissive device comprises an ultra-short throw projector.
 8. The displaydevice of claim 1, wherein a degree of scattering of incident light bythe electroactive element is based, at least in part, on at least one ofthe density or the average size of the nanovoids.
 9. A display device,comprising: an electroactive device positioned to be located at adistance from a user's eye when the display device is worn by the user,the electroactive device comprising: an electroactive element comprisinga polymer material defining nanovoids; and electrodes electricallycoupled to the electroactive element and configured to apply an electricfield to the electroactive element, wherein the electroactive element iscompressible from an uncompressed state to a compressed state by theapplication of the electric field so as to decrease an average size ofthe nanovoids and increase a density of the nanovoids in the compressedstate, a magnitude of the electric field associated with a desired sizeand a desired density of the nanovoids between the compressed anduncompressed states; and a waveguide display positioned to be locatedbetween the user's eye and the electroactive device when the displaydevice is worn by the user, the waveguide display configured to transmitimage light to the user's eye, the electroactive device positioned to atleast partially obscure a view of the user of an external environmentwhen in the uncompressed state.
 10. The display device of claim 9,wherein the waveguide display is configured to operate with a lightsource, the light source comprising at least one of a microlight-emitting diode, a light emitting diode, an organic light-emittingdiode, or a laser.
 11. The display device of claim 9, wherein: theelectroactive device is substantially opaque in the uncompressed state;and the electroactive device is transparent in the compressed state. 12.The display device of claim 9, wherein: in the uncompressed state of theelectroactive element, the nanovoids have a first average size on anorder of a wavelength of incident light; and in the compressed state ofthe electroactive element, the nanovoids have a second average size thatis substantially smaller than the wavelength of the incident light. 13.The display device of claim 9, wherein a degree of scattering ofincident light by the electroactive element is based, at least in part,on at least one of the density or the average size of the nanovoids. 14.A method, comprising: applying an electric field to an electroactiveelement of an electroactive device via electrodes of the electroactivedevice that are electrically coupled to the electroactive element tocompress the electroactive element, which comprises a polymer materialdefining nanovoids, from an uncompressed state to a compressed statesuch that an average size of the nanovoids is decreased and a density ofthe nanovoids is increased in the electroactive element, a magnitude ofthe electric field associated with a desired size and a desired densityof the nanovoids between the compressed and uncompressed states, whereinthe electroactive device is positioned at a distance from a user's eye;and emitting image light from an emissive device positioned such that atleast a portion of the image light is incident on an external surface ofthe electroactive device facing the user's eye such that the externalsurface of the electroactive device reflects at least a portion of theimage light toward the user's eye when the electroactive device is inthe uncompressed state.
 15. The method of claim 14, wherein: theelectroactive device is substantially opaque in the uncompressed state;and the electroactive device is transparent in the compressed state. 16.The method of claim 14, wherein an eyepiece is positioned between theuser's eye and the electroactive device, the eyepiece configured tomodify a focus of the user's eye to a focal plane of the electroactivedevice in an active state of the eyepiece.
 17. The method of claim 16,wherein: the eyepiece is a proximate eyepiece; and a distal eyepiece ispositioned near a surface of the electroactive device opposite theproximate eyepiece.
 18. The method of claim 16, further comprisingreducing the magnitude of the electric field applied to theelectroactive element of an electroactive device to expand theelectroactive element from the compressed state to the uncompressedstate such that the average size of the nanovoids is increased and thedensity of the nanovoids is decreased in the electroactive element. 19.The method of claim 14, wherein the emissive device comprises at leastone of an ultra-short throw projector or a waveguide display.
 20. Themethod of claim 14, wherein a degree of scattering of incident light bythe electroactive element is based, at least in part, on at least one ofthe density or the average size of the nanovoids.